bres dad, Years ago I had road bikes with crank arm lengths ranging from 165 mm to 175 mm. When I switched from one to the other I would notice the difference, but then after a short while I adjusted and the difference became unnoticed. All of my road bikes except for one now have 170 mm long crank arms. I took the 175 mm bike out Wednesday and didn't notice any difference what so ever. In fact I didn't even think about the subject. Because I transitioned easily between 170 mm and 175 mm crank arms I spec'd 172.5 mm crank arms for many of my builds.
When I needed a triple equipped distance roadie after the third injury to my left knee I spec'd a 175 mm crank set. I know it has more to do with a placebo effect, but I was able to put thousands of miles on that bike. My current distance bike is another triple equipped roadie with 175 mm crank arms.
Brad