More money doesn't always mean something works better. There is no question that Dura Ace is better quality in terms of better finish and sometimes lower weight, but the 7800 is an older design than the 5800, and IMO the newer design works better. Just like the 7800 works a lot better than my old Campy Nuovo Record single pivot brakes.

Those 5800s are really some of the best brakes I've used.

Ok Im sold on the new 105 spec vs the old Dura Ace spec, but I found an Ultegra 6800 front caliper lightly used for about $45 shipped. Any reason why I should still get the 105?

Yes.

It's not like you're getting a bad brake if you buy Ultegra or Dura Ace. Just pick one.

Even an inexpensive Sora is a decent brake. If you're a buying a mid-range+ brake from a major company, you're mostly paying more money for the next version to gain in tiny hair of weight savings/looks/possibly minor extra adjustment that most will not notice.

I learned that during my MTB days of converting multiple LX/XT parts to XTR and not really noticing any difference except for the XTR looked cooler/more street cred yo. The mid range LX was actually one of my favorite lines for pure consistency/durability.

Ok. Thanks for the info. What's advantage of the "direct mount" calipers? Do you need a special kind of fork to mount these?

Direct mount brakes are more rigid and aero, but require a special fork crown design and will not fit on a standard fork.

same here...

i agree with those endorsing the 5800 105's. I have front and rear on my SS and they are excellent !