Make the change for NVIDIA you wont regret! A lot of games have issues with AMD I can tell you that brutal legends is one of them, serious sam 3 is another, overall nvidia is a better choice at this moment. I just changed teams and bought a GTX660 and in some benchmarks it beats the HD7950 which is a beast of a card in windows.
It always depends on the apps/games/distro you run if you can live with amd gfx cards or not.
I dual boot. I have or usually have multiple operating systems installed. So, at any time, I'll have Windows 7, Debian, Ubuntu and I often try something like siduction and Kanotix in partitions. I might want to try Fedora 19 for kicks, too.
It's still between a gtx 650 and radeon 7770 for me. I found this:
This is very interesting if 2D and video playback works well with AMD cards. I like the idea of having the FOSS driver as a backup or maybe even the primary driver used. That's why I have delayed so long. I have a legacy Nvidia card or whatever you call it - it's not going to receive any more updates so I can't use newer Nvidia drivers.
It cannot be a long card so I have had to overlook the Radeon 6850, for e.g., even though that's probably one of the better AMD cards right now - at least, according to that GPU Driver Performance thread?
I am not a fanatic about needing FOSS but I must admit, not having to worry about the Nvidia driver update when you move to a new kernel etc. is intriguing. However, I haven't had to deal with the fglrx driver before and what if I'm not satified with the FOSS driver with AMD?
Anyway, budget is still under $100 so those two cards (7770 vs gtx 650) are what I'll consider. I'm just waiting to see if anything looks like it will change. The only other idea I had would be to buy a cheap htpc card and test the AMD driver. Then I won't care much if it's a subpar experience.
Basically for nvidia cards the best choice is to use xbmc as video player as this works fullscreen and has vdpau support. With the fernetmenta branch it works with xvba support with fglrx as well (but with limited hdmi passthru support under Linux). If you want to watch movies in a window a supported amd card with oss drivers looks better (has vdpau support for some cards as well for mplayer now but not for xbmc). For kde i still have to disable composite effects, but thats a general problem (intel and nv too), newer nv cards with kepler seem to flicker even then, if the opengl backend (which is of course not accellerated) is not used.