Hi aaaronmcd. My best "guesstimate" is the 165 crankarms are a benefit in reducing the amount of knee flex/angle. I don't notice this on the geared bikes. I ride 170mm on the geared bikes. At one time I had 172.5 on one of the geared bikes and 170 on another one and didn't notice the difference. But I think I notice the difference more on the fixed gear bike. I do 3-4 hour road rides on the fixed gear bike through rollers and grades and lots of wind sometimes. On the fixed gear my quads are my "gears" and with my really short legs the shorter cranks seem to be a benefit to avoid irritating the knees. On a geared bike I am a master of staying in the most efficient gear which I think avoids stressing the knees with the longer crankarms. I assume you are riding fixed gear if you are posting in this forum. If you are in SF Bay area I assume you have some real climbs to deal with. With 160 crankarms you will not climb standing as efficiently as with 165. A 160 crankset will be harder to find and maybe rather heavy if for recumbents. My recommendation is to go with 165mm and if not happy sell them and go shorter. For fixed riding I'm happy with the 165mm and wouldn't want to go shorter-don't want to lose power with each stroke and I spin fast enough as it is. Hope I answered your question.
Mike