Which side benefited the most from the new technologies during World War I?

Actually, both sides had access to the same technologies, but the main factor in the war would be their willingness and ability to use them.  In terms of battlefield technology, I will have to say that the Central Powers (especially Germany) were quite innovative in terms of their technology.  Germans were the first to use chemical warfare--actually, the first chemicals used were byproducts of industrial processes happening in German factories.  The German submarine sank a lot of Allied merchant shipping, driving up insurance rates for merchants selling to Britain and France.  German airplanes and pilots were often better during the war as well.  Technology is great, but does not win wars, however. 

In terms of overall technology, though, I have to say that the Allies had superior overall technology.  Within the first few weeks of the war, Britain cut the trans-Atlantic cable between Germany and America--this led to only the Allied side of news getting through to Americans.  Britain was able to use this by creating the story that Germans were massacring Belgians, thus creating anti-German sympathies in America.  When American war correspondents went to Belgium, they found no evidence of war crimes.  The Allies were also ultimately favored in naval technology, as the convoy system defeated the U-boat menace by 1918.  The U-boat menace was a double-edged sword for Germany, as it is hard to imagine Americans becoming outraged enough to join the war over the invasion of Belgium--it was the unrestricted submarine warfare that ultimately led to American intervention.  There is also the issue of Allied intelligence operations.  Britain intercepted the Zimmerman note which promised a Mexican-German alliance in order to distract America from the European war.  This intercepted telegram caught Germany off-guard, as they thought their diplomatic and military codes were top-notch.  

Finally, and this is the most important part of all, the technology that ultimately gave the Allies the edge was the ability to harness their own natural resources and make weapons quickly and efficiently.  American mass production techniques kept the Allies in machinery and ships as early as 1914.  American synthetic fertilizers gave the Allies an edge in terms of food production, as by 1918 the Germans were suffering a shortage of nitrates for both explosives and fertilizer.  The technologies of mass production and the ability to use faster, more plentiful ships to get product from America to Europe ultimately gave the Allies the edge, despite the innovations which came first from the side of the Central Powers.