Ive never owned bikes that are the same size, im also 5'9" and right now have three bikes that are three different sizes so i think it depends on the bike. If you are unsure of size you want or need, internet buying may not be for you. Or go to LBS and test 5 or 6 bikes all different makes if poss. and just kinda average them out. I have a 17", 19.5" and a 22" and each one of them "fits" me.