My strong suspicion (without seeing the complete build) is that you don't need anything more than a Seasonic X-560.
M., I support your comment but one can extrapolate from this.
(Sorry, J., I cannot comment on the two specific ones you are asking about. Maybe another member can. Just some general advice from an experienced builder.)
Any mid range power supply is probably enough, so you should be looking at features such as reliability, warrenty, cable modularity, effieicnecy, and even the paint design if you have a "tie" or a side window.
But more important if you are at SPCR...noise.
For noise reasons, if you buy a P/S over-rated for your system needs, you will never have to use it above base RPM for the Fan (I use 50% max load on the P/S as a personal guideline). What I did on my last build was retrofit the fan in an old P/S at 2X needed power rating with a nectua 120, down volted the fan, and I can't hear it ever. Newer P/S have better fan control, so may well be quiet enough without fan or voltage change.
Read the great build articles from late last year, they discuss P/S choices, at http://www.silentpcreview.com/Silent_Home_Server_Build_Guide
I Like your choice of CPU for you build, this what I will use for my build # 12, for my wife.