Here are some interesting results on tire performance. Go wide, go vulcanized...
Karl

Here's another one. Already on 25s , thinking about going to 85psi
http://www.cyclist.co.uk/in-depth/726/are-wider-tyres-really-faster

Something interesting to note: manufactures normally test tires on a smooth drum, at max pressure, which doesn't simulate suspension losses. A narrow, high pressure tire will have a small contact patch that will deflect (bounce) over road surfaces. A wider tire with a larger volume and lower pressure will deform and roll right over changes in road surfaces, especially if the tire has a supple casing. Back in the 1950's, French randonneurs were quite aware of this, riding low pressure 42mm 650b tires on roads that today's "roadies" wouldn't dare, with competition results that came close to making the pros look bad. Editors of Bicycle Quarterly (with engineering doctorates) have done several road tests confirming this. Professional racers at Paris-Roubaix are on 30mm sew-ups at 70psi.