Hey all - I just went for my first ride on some Conti UltraSport in 700X25, and I can't believe how smooth they feel! I had been using UltraGatorSkins in 28, and the difference was substantial. I'm really tempted to run 28c UltraSports instead of the Gatorskins I currently have on my commuter. Question is, how much flat resistance would I be giving up?

Cheers, thanks in advance...