05 kawa 636 FTW....seriously though, I've also sat on all of them when i got my 636 2yrs ago and performance/ comfort wise, the 636 beats them all hands down. all my friends had gsxr's 600's and 750's and id beat the 600's and stay right with the 750's. That was stock before I got the 2brothers underseat exhaust so i dont know howd they match up now, def. better though.