Joined: Dec 2009
Posts: 1,808
Likes: 188
From: Denver area (Ken Caryl Valley)
Bikes: 2022 Moots RCS, 2014 BMC SLR01 DA Mech, 2020 Santa Cruz Stigmata, Ibis Ripmo, Trek Top Fuel, Specialized Epic Pro, Pivot Les Fat
Well, my 25s measure 28 so I'll vote for 28s.
EDIT- I don't know if they are faster everywhere. On rougher roads, I do think they are. On smoother roads and especially long climbs, I think 25s are slightly faster though not by much. The 28s are faster on those same descents so it is a wash. I'll go for the comfort on the 28s given my bike has no Iso Speed etc anyway.