I'm in the process of speccing up a New! Shiny! bike. Traditional steel, with lugs, like god intended. Light touring, hopeful audax, that kind of thing. I'm mithering over the choice of groupset. The bike it replaces had a mix of 105 and Tiagra with a Spa cycles triple chainset.
I understand 105 is only available in 11 speed, which is a bit new fangled for me. Tiagra is 10 speed in double or triple. From what I've read so far, Tiagra isn't far behind 105, if at all, in terms of performance, with the possible exception of braking. I suspect the current Tiagra brakes will be better than the mix of 17 year old 105 calipers and 105 5703 levers though.
I don't like the look of external bearing chainsets on a traditional frame. Am I dismissing a superior technological solution on aesthetics? UN5x bottom brackets Just Work.
Having got that waffle out of the way, what does the panel think? 105 or Tiagra? Or other? Square taper or external bearing? Shimano chainset or other (Spa for example)?