#1: The 80+ Gold is better than the 80+ Bronze. It just means that over 80% of the power is being evenly distributed.
#2: Pros for XFX: Price, semi-modular, and it looks freaking EPIC! Cons: It's not 80+ Gold (but it's silver, not bronze.)
Pros for Seasonic: Price(once again), Semi-modular, a lot of cables
Overall I would go with the XFX because it looks cooler and it's pretty much the same as the Seasonic.