I'm 5-11, 32" inseam. I have 172.5mm cranks on my roadbike, and 170mm on my TT bike. I would probably go with 170mm if buying a new crankset for my road bike today. It's not a hug difference, but it's there: a little more ground clearance, a slightly more open hip/knee angle. Plus I tend to prefer a fairly high cadence. Extra torque for mountain ascents isn't something I have to worry about here, the short rollers we have don't even require using the small chain ring for the most part.