I'm aware that as almost everything, it's a compromise. But for my riding (speed+roads+level) I would probably be faster on a 28C. I'm not questioning if a 25C tire is faster on good and smooth pavement, I fully understand the physics, but for me a carbon-framed bike with good geometry will deliver the most amount of fun if on 28Cs. Of course, if I can get away with 25Cs in terms of comfort, I'll opt for the faster tires obviously, but I really doubt it.
And PS: You guys drink way too much - do you use hydro packs? I need 700 ml every 30 km.
if you're not a competitive racer, this is the only metric that matters.