How much of a difference will going from 170mm crank to 172.5mm make?

I've been using (and dialed in with a pro fit) 170mm cranks for the past five years, but a riding buddy is selling his grouppo for a good deal with 172.5mm cranks. Too much of a difference or no big deal? Pros and cons, and what should I be then adjusting on my set up? Thanks.