First, even thought the cranks are Powercranks this is NOT a powercrank thread. Second, I have only done 2 rides so this is just some initial thoughts. No tests, no conclusive data, etc.
I am short (5’6 on a good day) with short legs. I normally ride 170 cranks on my Tri and road bike (both 51 Cervelos). I had some old 172.5 fixed length Powercranks and riding them could be done but PAINFUL. Got the new model that allows for crank length adjustment. All rides are on the computrainer. Rode a couple of times with the normal 170 length on the road bike. Was good but was tough to maintain faster cadences on the PCs. Switched to 165 length for next ride. MAN … what a difference this made. Instantly more comfortable. I also raised my saddle commensurate with the shorter crank length. Next ride I went down to 160. WHOA! At first felt SO WEIRD. But then I really really liked how the 160s felt. Much Faster cadences and more comfort. Incredible feel. I am hopeful that this will help me stop meing a masher and help with comfort.
I will run some numbers tests in the next few weeks and report back.