No functional difference. Leather is thicker on a Brooks 'Pro' than the others. Mine is honey color, and after treating it with proofhide, riding and sweating on it, has turned to a rich, silky, milk chocolate color that is truly beautiful. The only bad thing was that somehow it permanently stained the side of my top tube close to the seat stay lug, right on the "Irio Tommasini" signature. I guess it had to of come from my shorts somehow. I had to use some rubbing compound to get it off.

It's not bad now, but it's still slightly discolored some.