Keep in mind we are talking about a very small difference. For CDR's distance traveled it's 1.5% change. So your foot speed is equal at 95 rpm on a 175 and 96 rpm on a 172.5. I've run everything from 165 on the Track to 175, and while you can feel the difference it's very subtle. I really think within the "normal" range for road cranks it's nothing more than personal preference, with a dash of placebo effect and a pinch of what you are used to.