It doesn't alter comfort, but IMO fixes and tracks look better without all that extra touring bike-y leather. Of course, you could go out and buy a Swift or a Swallow, but you can get the same vintage (...yes, vintage. Trimming a B17 or Pro is nothing new, and even if it were, Swifts and Swallows have been around for quite a while) look for a fraction of the cost. And seeing the rails gives the impression of a slightly longer post/higher saddle, as well- another benefit. I use a regular B17 on my geared "everything" bike, but a nice track frame deserves a thinner saddle. You do want to consider weight (yours, not the bike's) and possibly thigh size if you decide to do this- just make sure not to cut off too much. It's also better, IMO, to do this to a new saddle than a broken-in one. I wouldn't mess with one I liked.