OK, let me add "big tires run at the conventional pressure (80ish PSI) compress more than skinny rigs at 120ish, so you're not necessarily going to be sitting 10mm lower on a 25 than a 35." A larger volume tire always has a larger contact patch even at the same pressure, and the contact patch also gets much larger under increased loading, so actually pressure doesn't really matter. Also, I only run skinny stuff now after years and years of running 26 x whatever, 27 x 1.25, and 650B x 35, I know what I'm talking about here. A bigger tire at a lower pressure is more rolling resistance any way you slice it, not to mention inertia. I ride long distances in urban conditions, some might want fatter tires for comfort but I'll take speed, agility, and acceleration any day. I achieve comfort by paying attention to what I run over, and other than snow pack where I wish I had MTB fatties I'm happy with them under all conditions (and in Chicago, we get all conditions).

You can roll over to the rivendell page if you want to read the real arguments in favor of fat tires, but the first premise of everything over there is "speed doesn't matter."