I've heard nothing but bad things about OCZ power supplies. If there is one component in your system you don't want to go cheap on, it would be the power supply. That said, XFX has a pretty good reputation with their power supplies, so I'd suggest going with that one rather then the OCZ one.
EDIT: For an additonal $10, you may want to consider the
Corsair TX750M. It's a semi-modular PSU, so you're getting the best of both the OCZ and the XFX PSU's you mentioned. NCIX doesn't have any pictures, but there are some of the unit over on
Newegg.ca.