"SLI and CF are actually really great bro IMO experience with them the only difference was allot more performance and the need to DL some hot fix drivers to enable the dual cards in some Brand new games when they first came out. PS would you even use CUDA if going to Nvidia ? and how many games that you own actually have Physx ? and AMD drivers are really solid I have just as many issues with my Nvidias. "
- SLI/Crossfire. It can work okay but just be aware there are PROS and CONS to this. For myself the Cons outweight the Pros. Here's a really great article:
http://www.tomshardware.com/reviews/radeon-geforce-stutter-crossfire,2995.html
*Note that the new HD7xxx cards can turn off almost 100% of the second card (or the second GPU for a dual-GPU card).
- DRIVER SUPPORT. The general consensus appears to be that NVidia is quicker for new games and in general is a little better. I've been very happy with my HD5870 so, I guess... whatever. They are both pretty good.
- PHYSX.
No. I don't use it (I have an HD5870). In fact, since PhysX has a big hit on performance I wouldn't have used it in any game that brought my frame rate below 60FPS. If I can get 60FPS and PhysX adds a little eye candy then sure, I'd then use it.
Basically, everything being equal, PhysX would tip the balance. (I'd rather have it and not need it then need it and not have it.)
- CUDA:
I convert a lot of videos. I have several thousand of raw conversion hours of work left to do and my CPU (i7-860) uses all 8 threads at 100% when converting. So I'm hoping a GTX680 will be a huge help.
FYI, the OPENCL initiative is still progressing (basically about using both the CPU and GPU for processing at the same time). I've seen no indication that a good video conversion program will be ready in the next two years using OpenCL so the main option still seems to be CUDA (and Kepler supports OpenCL as well).