Corsair I believe has a 7 year warranty and the Seasonic has a 10.
The Corsair underneath is the exact same as the Seasonic as they supply them as an OEM. Only recently Sea Sonic decided to release it themselves. Might also be cheaper.
Also if anyone reading this is thinking of the EVGA or Corsair in a 750W or higher just go for the SeaSonic since the PSU is shorter than the other two and better.
Well i might go for seasonic because its only focusing on creating psu's and its 3 year more warranty.But the rmx its 15-20 euros cheaper than the seasonic, with much more reviews (rmx)
Seasonic, would always choose Seasonic over Corsair if the option is there. For that system though, you might as well just get an S12II 520W. Cost effective yet quality. I run one myself, 4 years still kicking