Originally Posted by
Bah Humbug
Especially for certain components there is little to no difference. Front derailleurs get slightly lighter but don't work differently, while rears have more of a weight difference (for whatever it matters) and can be snappier, especially going from a low-end to mid or upper. On the other hand, from what I have read the early 6700 shifters tended to fray and cut shifting cables due to an engineering issue that was rectified for 5700, making the lower-end option preferable of those two.
Over in Campy-land, going to Chorus shifters instead of Athena allows more gears to be shifted at once in each direction, and the crank gets an appreciable upgrade as well.
Now, how much all this means to a recreation rider is an entirely different question.
Disagree about FD especially the DA 9000 FD. That thing is beautiful, shifts are as easy as rear shifts, even going up to the big ring. The new design and shift operation is totally different than other Shimano stuff. Two trim positions for each ring as well. It's way different, and a major improvement.
I had 6700 stuff, and it was a step down from 6500, especially the shifting. First gen under-tape cable routing for the Ultegra line and it showed. Much cleaner looking, but practical operation was not very good. Shifting up on the FD was really stiff.
But the DA 9000 group is ridiculously good. You can certainly argue the value and pricing (I got a price that I felt comfortable paying), but the operation is a massive improvement to anything I've used before in the Shimano line.