You can read Bicycle Quarterly's take on the subject here:

http://www.vintagebicyclepress.com/i...64TireTest.pdf

Fwiw, the key is good tires, whether skinny or wide. As USAZ points out, the Grand Bois tires are like riding on fast clouds, and I push the 30mm version around. But my favorite ride currently is on my 584mm x 41mm Hetre tires on my Ebisu, pumped to 50 psi.

Neal