It is probably just in my head, but I swear I can feel a 175 vs. 170 (all things being equal).

I am 5'10" and run a 56cm frame (typically) and 175 just starts to feel right with my leg length, that sounds awful long for that size frame as posted above-


Edit to add- When I started cycling, the commonly available cranks were 170's and 172.5's if I remember correctly, all these crank length choices are relatively new in the cycling world. I wouldn't get too wound up about crank length (no pun intended).

I went to 175 just to try it out, adapted to it, and have run it since.

As to the cranks, Dura-Ace is some awesome stuff, I always thought that FSA was the "poor mans" Shimano 105?