Some comments I read: longer crank arms might mean some knee soreness for some people and will mean less "leverage" for going faster. I mean if someone wanted to go fast with 52T front chainring and 11T cog in the rear, 170mm cranks would be faster than 175mm. I did read one comment of someone stated he felt liberated with 175mm cranks and wouldn't go back to 170mm.

Part of me believes if going with what is recommended though. I was measured in a store at 83.5cm inseam (32.8 inches) and I'm 5'8-1/2"or 174cm so I'm guessing you measured manually and not on a machine. I've seen 172.5mm recommended for my inseam/height but since I have a bit of chondromalacia in my knees, I think I'm going to stick with 170mm. For whatever reason though, for my long legs, I often feel like longer crank arms would "let me breathe" although I don't want to risk installing 175mm or even 172.5mm on a bike.