cynic-al - MemberShrug - it's just the other side of the coin to what you're saying. As you know, there's an awful lot of bolloxology in the bike business, with a lot of the comparisons you read on here being pretty meaningless to the point of straining credibility - what travel for my BFe, 120 or 130mm? XC racer compares 29er v 26er and is 15 secs a lap faster; the new ragley piglet Ti only rewards the forthright rider; How can I drop 200g from my wheelset? etc etc
So Garry...the tire makes the biggest difference, oh hang on, is it just how worn it is? But bikes don't really matter...?
ITSM that the design, size and construction of your rubber does actually have some substance to it and some very meaningful distinctions can be drawn.