Need help with deciding the next graphics card to get....

I am usually strictly Nvidia but have been looking into getting an ATI (specifically a Radeon 6790, my old card is a GTS 250). So I wanna know what you guys opinions are of Nvidia vs. ATI like pros and cons (not trying to start an argument, everyone is entitled to an opinion lol). I just wanna know what based on your experiences I should get I would like to stay in the 150 dollar price range though. I would also like to know what brands are good like EVGA (which I decided is pretty much what I will go for with Nvidia if I go with it again), but I pretty much wanna know what the best brand for ATI is (like I said feel pretty strong about EVGA for Nvidia based on what I hear) like is XFX good? I run an AMD system by the way (Athlon II 635 Propus 2.9Ghz with 4 gb of ram and 2 500 gb hard drives with a 700 watt power supply)