780 or Nvidia? What am I missing?
I was Nvidia, then used an ATI (I think they were still ATI back in the 5870 days?) and then went back to Nvidia. I've just recently gone back to AMD cards.
Although I didn't really play a lot of PhysX games I was a bit concerned about losing the option when going to AMD, just in case a game I wanted to play did make good use of it. It's still a bit of a concern. I didn't try playing the PhysX games I did play without PhysX, so I'm not sure what difference it made.
I think I'd probably be the same with regards to Mantle if I get an Nvidia card in the future.
As I think someone else mentioned, I often tend to buy 2 cards these days (once you go multi-GPU it's hard to go back to 1 I find) so I don't think I notice the hit of PhysX on performance too much. In the same way I'm also not sure I'll see much benefit from Mantle.
I really just buy what takes my fancy at the time. Recently I decided that since I buy 2 cards it works out cheaper with AMD. I also felt like trying AMD as AMD owners seem to think they're very good, so I thought I'd try them.
I know some people are firmly in one camp or the other, for whatever reasons, and so probably already know if they're next GPU will be read team or green team. I just buy what I like at the time, I couldn't tell you what my next GPU would be, I'm already looking forward to it though!
EDIT:
The other thing that tempted me to try AMD was that my monitors don't do Nvidia 3D Vision but do work well with AMD 3D via TriDef. Since I bought 3D monitors I wanted to try it out. It's nice, but doubt it's enough to affect my next purchasing decision.