I didn't like how C-3PO was present throughout the prequel trilogy, it seemed pointless to me making Anakin his maker and be with Padme the entire time, only to have his mind wiped and in the old trilogy have him end up with Lars twice and in the possesion of both Skywalkers (although Threepio is in Han and Leias presence 90% of the time). R2-D2 on the other hand I never complained about, it was fitting for him to be in the prequels. To me Artoo is much more than your average astromech droid, he's more like a "guardian angel" of the Skywalker family, and eventually the Solo family as well. He aided Anakin before he fell and then became Luke's droid. All the while this unusually intelligent and rebellious droid is very capable and seems to make the right decision everytime, always having a trick or a trump card in his metal casing. R2-D2 never has his memory wiped, so he remembers everything from Episode I-VI, which I think is the most important factor in my "guardian angel" claim, and is also important for Luke and Leia to finally learn about their mother and father, deep within Artoo's computer core.