I'm going to disagree (maybe it's just because I'm taller I guess), but I definitely would feel a huge difference between 170 and 175 cranks. I feel a large difference between 172.5 and 175s.

Whether or not this amounts to anything in terms of performance- who knows. I'm sure I could get used to 172.5, but I started cycling with 175 and now anything else feels odd.

Go with whatever's comfortable.