I reasoned that I should have longer cranks, based on my height compared to "average." I'm 6'-2" and the average cyclist is 5'-8", or whatever, so by simple proportions I decided to try 180's. They are scarce. I put 180's on both my road and time trial bikes. I rode and raced on 180's for several years. I still had 175's on other bikes.
The left 180 crank arm broke on the road bike (causing permanent injury, by the way) and then I sold off the TT bike.
Going back to 175's I could not tell the difference.