I use 175 mm cranks on the road and had a winter bike with 170mm cranks. I could definitely feel the difference, and I tended to pedal a cadence of 5 or 10 rpms higher with the shorter cranks. So, in the name of specificity of training I put 175mm cranks on the winter bike. When I got a track bike with 165mm cranks for winter training, I made the same switch. It makes the transition back and forth from bike to bike feel less weird.