I've used Gatorskins in a 26x1 1/4 size for commuting in NYC and they were the best for me. Relatively light, decent flat protection, and dare I say it, fast. Last year I was planning on using this bike to ride the Empire State Trail from Buffalo to NYC so I put on the pair of Schwalbe Marathons that I had in a 26x1.75 size. I did some test rides with them with loaded bags and figured they'd be fine. I never did that ride, and this year they were still on the bike and I was taking it on short trips and it always felt like a slog. The other day I put the Gatorskins back on and the difference was night and day. I could get the bike moving again without a huge effort. I ride with an HRM and computer (bought for my road bike, but I also use on this) and my HR is way down now.

I compared the weights of the two tires, a Marathon is 740 grams while a Gatorskin is 320 grams, almost a full pound different. That's a lot of extra rotating weight. If I ever do the trail I'll keep the gatorskins on and carry an extra, that's still a lot less weight than the Marathons.

Don't let anybody tell you fat tires are just as fast as skinny ones.