Performance wise the Ultegra will roll longer, better bearings = less friction. They'll spin up faster too.
Stronger hamsters?Do they definitely have better bearings though?
This is what I've mostly heard. Yesterday's Ultegra becomes tomorrow's 105 anyhow.The Ultegra ones are a bit lighter and say "Ultegra". In terms of performance and longevity there's not a chocolate mouses pube in it. It's an improvement in weight and finish for a.corresponding increase in price.
The only claim that Shimano themselves substantiate is that it's lighter...
http://www.shimano.com/publish/cont...ad/ultegra/product.-code-HB-6800.-type-..html
http://www.shimano.com/publish/cont...ad/ultegra/product.-code-FH-6800.-type-..html
They make no claims that it rolls any better than 105 or Tiagra, and certainly don't publish any technical data that proves such a claim.
It's a bit lighter and has a more attractive finish.