The Block-Schwenk Collective 
What was special about the Christmas Truce of 1914?
What was the ultimate result of the German U-Boat (submarine) campaign?
The short answer is yes, the Germans were better soldiers: better trained in the areas that mattered, and better equipped.
Because the Germans had taken most of Belgium and part of France, the Allies were politically compelled to attack, while the Germans could attack or defend based on military factors alone. While the allies eventually found ways to attack successfully, it took much time and hundreds of thousands dead to learn this.
Another consequence of this compulsion to attack was that, while the Germans could fortify their efforts into making their line as impregnable as possible, the allies always viewed their trenches as temporary places to stay before the next big push. As a result, German trenches were of much better quality. For example, most allied trenches lacked holes for the soldiers to shoot through without exposing their heads, known as loopholes. It is questionable whether the moderately successful German attacks of the spring of 1918 would have succeeded at all versus German-qualtity defenses.
There were other factors as well:
Uniforms and helmets: In 1914 the German uniform was "field gray" one of the most difficult colors to see. The British wore Khaki, which wasn't bad, but the French still had their 19th century uniform of blue with bright red (the most visible color in existence) pants! Also, unlike the Germans who attacked in 1914 wearing the famous spiked helmets, most British soldiers did not get helmets until early 1915, while the French did not get helmets until late 1915 (and most Russians never got them). By the end of 1915 this was no longer a significant difference.
Weapons: German divisions had nearly twice as many machine guns as did those of the Allies. Both sides rapidly increased the number of machine guns throughout the war, but the Germans maintained this lead. The allies did develop tank in large numbers, while the Germans did not, but this did not happen until late in the war.
Training: A great irony of both world wars is that the generals of the autocratic German state trusted its soldiers far more than the generals of the democratic allies. German lieutenants and even regular soldiers were expected to show initiative and, make important decisions, and quickly exploit opportunities that presented themselves. The allies, particularly the French in 1914, and the English and Americans throughout the war, had a very top-down command structure, in which only high-ranking officers were to make decisions. Because communication was slow, this meant that many small fleeting opportunities were lost while soldiers stopped and waited for orders.
Participants in WWI
Allies who fought from the start:
France, Russia,
British Empire (Great Britain, Canada, Australia,
New Zealand, India, South Africa)
Central Powers who fought from the start:
Germany, Austro-Hungarian Empire
Japan, Italy, Portugal,
Romania, The United States
Countries who later joined the Central Powers:
The Ottoman Empire (Turkey), Bulgaria,
many colonies.
On Christmas of 1914 on the Western Front, particularly the British sector, the shooting stopped. In places soldiers even emerged from the trenches to bury their dead; trade souvenirs; sometimes sing Christmas Carols; and, it is rumored, play soccer. This was dangerous business: some were killed by fire from other parts of the line. Where this happened, the informal "truce" often held for several weeks, until soldiers on one side or the other were rotated out of the line, then the war resumed, although neither side was prepared to undertake a serious offensive in January of 1915.
The Christmas Truce of 1914 is often viewed as miraculous-a day when soldiers on both sides said no to war, as though the people of belligerent nations had discovered each others humanity and were one step away from going home. In fact, what is more notable about the Christmas Truce was that it took place in less than half of the line, was much more rare in 1915, and nonexistent in following years.
In the centuries prior to World War I, truces of this kind were the norm. In the small wars of the 1700s, soldiers regularly went to a river to wash their clothes, fill their canteens, and so forth, often with "enemy" soldiers directly across the river. They would typically ignore each other. Fighting was just their job, so why risk getting killed when you didn't have to?
Even in conflicts where there was ideological conflict, such as the American Civil War, temporary truces were the rule. For example, after the terrible slaughter at Cold Harbor in 1864, a truce was called for both sides to bury their dead. Union and Confederate soldiers came forward, worked next to each other, and again, traded souvenirs.
Prior to the Twentieth Century, with a few notable exceptions, armies only campaigned during good weather, going back to camps and not doing much during the winter. Thus, there were informal "truces" that lasted for months. World War I changed that, in that soldiers were expected to stay on the front lines every hour of every day.
World War I was the first Total War in centuries. Total War is where the entire population is mobilized to fight. While the lower-class soldiers of the 1700s would fight simply because it was their job, the educated citizen-soldiers of the Twentieth Century had to be taught to view the other side as enemies deserving death.
The British army of 1914 (what was left of it) still consisted of mostly working-class professionals, who felt little personal hatred of the Germans. Unlike France and Belgium, England was not invaded. Germany was similarly not invaded. The Truces were more common among parts of the line where there had been less heavy fighting. Furthermore, both sides knew that there would be no serious attacks during the heart of the winter, with both armies exhausted by the fighting of September-November. So why not have a little pause from the daily misery before the war resumed in earnest?
By 1915, most of these professionals were dead, replaced by former civilians. There had been too much death, and sides were more likely to view each other as "the enemy." The high command on all sides also actively discouraged fraternizing. There were some truces, but they were rarer. By 1916, this new way of thinking was total. The last vestiges of an earlier, less hateful type of armed conflict had been cast aside.
Although fraternizing had ended, informal truces continued throughout the war. Many units, particularly French-German later in the war, and units on the Eastern Front, adopted a "live and let live" policy, in which neither side would routinely shoot at the other.
The winner of the War at sea was, without question, the British (and thus the Allies).
To determine the winner, one should not look at how many ships were sunk. (The allies lost more ships to enemy fire.) Rather, one should look at the purpose of a navy, and whether or not the navy accomplished its purpose. Ultimately, the purpose of a navy is to make the ocean safe for its own merchant and transport vessels, while denying the use of the oceans to vessels of the opposing side. The British navy accomplished the former reasonably well, and the latter to a degree that was almost total.
Within a month, merchant ships of the Central Powers had all been captured by the allies, interred for the duration of the war in ports or neutral countries, or at best, bottled up in their home waters, unable to venture outside the Baltic Sea. Ships of the allies, on the other hand, could sail over the entire world.
Although "freedom of the seas," otherwise known as the right of neutral countries to trade with belligerents without interference, was guaranteed by international treaty, both sides of World War I cast aside this concept in favor of blockade.
The allies imposed a blockade on the Germans, forbidding neutral countries to sell "war materials" (which translated to just about everything, including food). This allied blockade, run mainly by the British against the Germans, was performed by surface ships. As a neutral ship (most notable and commonly American) approached the Baltic, British warships would intercept it, board it if necessary, and order it to England. The cargo would then be taken. To assuage any hard feelings, the British would then pay for what they took. Although Germany managed to import some war necessities, most notably large amounts of fats (used in making explosives of all kind), via neutral countries on its borders, and Germany was less dependent on sea traffic for what it needed, the German economy was damaged by the blockade: industrial output fell during the war, and the people were hungry enough to be very unhappy and vulnerable to disease.
As to warships, the Germans had roughly 2/3 as many heavy warships as the British. The Kaiser did not want to risk his navy, so the German navy never tried to seriously break out of the Baltic. Several small engagements were fought, none of them decisive. The one time the full fleets clashed was in the Battle of Jutland, off the coast of Denmark. The British lost more ships, but neither side lost very much, and the battle ended with the German Navy fleeing toward its home ports, where it stayed for the rest of the war.
The Germans attempted to impose a blockade on England, which was far more dependent on sea traffic. However, as noted, the German navy never broke out of its home waters. At the beginning of the war, Germany had a handful of commerce raiders scattered around the world, but these were quickly hunted down and either destroyed, scuttled, or interred in neutral ports.
To impose a blockade, Germany had to rely on one weapon: the submarine, otherwise known as the U-boat. The problem with submarines is that they are extremely small, weak vessels, vulnerable to the sorts of guns often put on merchant ships. Thus, submarines could not board vessels, capture vessels, or redirect them. The only thing submarines can do is sink vessels by stalking them underwater and launching torpedoes.
Any anger Americans and other neutrals felt at Great Britain for forcing their ships to sell their cargoes to the British was quickly eclipsed when ships started to get sunk by German U-boats.
In 1915, soon after the Germans began a campaign of "unlimited" submarine warfare (= considering any ship within a certain of radius of the British Isles a legitimate target) the Lusitania, a British carrying ammunition in its cargo bay, sailed from New York to England, with over 1000 passengers, including 200 or so Americans. The Lusitania was sunk by a U-boat, with most people losing their lives. The American government, defending what today would be considered the absurd right of Americans to be safe while traveling on ships belonging to belligerent nations which were transporting ammunition. [Link At the time the British denied that the Lusitania was carrying ammunition, and it was not until over 50 years later that the government admitted that it was doing to.). The United States threatened to declare war against Germany unless the U-boat campaign was suspended. In the face of this threat, this happened.
In early 1917 the German commanders decided to resume unlimited submarine warfare, with the full knowledge that it would bring the United States into the war against them. They gambled that, deprived of imports, the British economy would quickly collapse and England would pull out of the war, thereby allowing the German army to quickly overwhelm that of the French. Resuming unlimited submarine warfare indeed brought America into the war, but the British economy did not collapse. Indeed, once ships started sailing in convoys, losses shrank to less that new ships launched.
Thus, the German U-boat campaign was a colossal failure. It brought the United States into the war on Germany, in exchange for no significant military gain.
Apart from a bit of scouting, spotting for artillery, and shooting down each other, not much.
Aircraft bombed both soldiers and civilians, but with neither the quantity nor the accuracy to be militarily significant.
Ironically, the most significant role played by aircraft in World War I occurred only 1 month into the war, with the air forces of all countries were tiny. French aircraft discovered a gap between the two westmost German armies. Allied armies charged into that gap, and the ensuing battle known as the Battle of the Marne, in which German forces were thrown back from Paris.
Despite the relatively insignificant roles played by aircraft, fighter pilot aces of World War I are more famous than those of any later wars, the most famous being Manfred Von Richtofen a.k.a. the Red Baron.