Originally Posted by
WalksOn2Wheels
Because of the way that Shimano works the trickle-down tech there are 105 groups that are basically identical to the previous gen Dura Ace, so they are essentially the same if you compare the right groupsets.
They are getting *very* close, now. I haven't looked at the non-hydro stuff, but within the current groups, you're looking at stuff like: paint vs anodized, aluminum vs carbon levers, the ability to alter brake engagement, slightly better bearings in the RD, etc. Oh, and a couple hundred grams or so. IOW, in terms of function and performance, there's almost nothing separating them. Vanity and weightweenie-ism will keep the Ultegra and DA selling, though.