Evga > RM series all day every day. Evga can do no wrong since they went with Super Flower as their OEM of choice.
Bah, they are both perfectly capable PSUs. While EVGA outsources their manufacturing to Super Flower, Corsair uses Seasonic, which is no slouch in the PSU industry on its own.
Corsair also consistently ranks high in JonnyGuru testing as shown here with the Corsair RM1000x receiving a perfect 10.
http://www.jonnyguru.com/modules.php?name=NDReviews&op=Story6&reid=449I love EVGA too, but there is no need to preclude another perfectly good brand just because of some bias. I have owned and will continue to own both brands. I have also had to RMA power supplies from both brands, with both offering excellent customer service and a no hassle RMA process.
In reality you really cannot go wrong with either brand, just get whichever one is on sale at any given moment that suits your needs.
One final note, once you start looking past 5-6 GPUs you really should start to consider using a server PSU with a breakout board, as they are better suited for large rigs and can deliver the wattage you need from one unit using 220V input. Their pricing is also very competitive with the higher end consumer PSU's, especially considering the fact you would often need utilize two consumer PSUs once you go past 6 GPUs.