The XFX P1-650S-NLB9 is a higher tiered model, made by Seasonic, and beats the FSP in quality, if not efficiency. The XFX can put out 53 amps compared to the FSP 46 amps. Both have 5 year warranty.
I would opt for the XFX because it's built on a Seasonic platfrom and is very well reviewed. It falls under Tier 2 of Tom's PSU chart where as the FSP is a Tier 3.
The XFX P1-650S-NLB9 is a higher tiered model, made by Seasonic, and beats the FSP in quality, if not efficiency. The XFX can put out 53 amps compared to the FSP 46 amps. Both have 5 year warranty.