I run (ran?) 52x18 and while I don't necessarily get the same RPMs as shorter gears, I don't tend to have any trouble powering it. I've always preferred bigger gears, I guess. But then, Chicago is pretty much flat. I probably wouldn't be riding 52x18 if I was still back in the hocking hills in Ohio, though. Not unless I got stronger, anyway. Ultimately just do what feels right.