I'm 6 feet tall, with a 32 or so inch inseam-- I ride a fixie with 165s, and two road bikes with 172.5s. Can I tell the difference? probably, but its not really noticable. A riding buddy did comment on the fact that on my fixie my knees don't come up nearly as much-- go with what feels the best, or stick to what you have, and use the others fo r specialty items-- the fixie has 165s to reduce the chance of 'bottoming out' on your down stroke when going around a corner--you can't contrpl which leg is up or down, as you can't coast on a fixie. That is why track bikes tend to have slightly higher bottom brackets and shorter cranks.