I agree with pretty much everything said so far. I was commuting on a 25" fixie, now I am on a 23". There was no problem nutting myself and there was no standover clearance. The handlebars were a little far away. With the 23" the seatpost was too short to get the saddle up high enough, and I lived with it for daily commuting ( 26km roundtrip) and then I started having knee pain in several weeks. Don't do that! I got a new seatpost and now all is good. All other things being equal a smaller frame will be more stiff and lighter.