My bike is a very small, wsd, and originally came with 650c wheels and 165 cranks--but I swapped them out for 170s when I bought the bike.

There's considerable toe overhang with the 170s, so when I decided to get a compact crank for hill climbing, I went back to the 165, but even with the compact crank, they don't seem to work as well as the 170s with 53/39 chains--not even for climbing; the same leverage just doesn't seem to be there, and even with 165s, there's still a certain amount of overhang.

So I'm sticking with the 170s. If I run into any really bad hills, maybe I'll get a triple, but so far hasn't been necessary.