summed up the whole thread right here. that's the biggest thing i've noticed. i went from 175 to 170 and haven't noticed much, but when i'd go from 175 to 165 on my friend's bike, it'd be a fairly noticeable difference. i'm happy with the 170 right now though it is true at higher cadences, a smaller arm could but a little more comfortable, but i definitely like the leverage for hills.

if my city were flat though, there'd be no question about going 165 or even 160 if i could find it.