Another major difference between nVidia and ATI is the driver handling.....
I favour the nVidia way of driver handling.... 1 driver to handle the card.... that includes the 2nd output (i.e. TV)... since most cards compile the graphics for a 2nd output in ANYCASE whether you use it or not, this helps a lot to improve the throughput on the card (since 1 pic is processed only ONCE for both outputs)
ATI installs 2 drivers for the card (one for each output).. so 1 pic will be processed for output 1 and then processed again for output 2.... this is a handy feature when you are stretching desktops, but a big slow-down when you cloning or extending.... Most people i know clone their desktop, even if they dont know it (2nd output not connected).
As for the SLI cards (Duel processing).... very handy.... when you have the right games for it... or do video rendering. It pretty muchly SHARE the workload of the cards, depending on how the game gets handled through windows, you can either have 1 card doing a section of the screen and the 2nd the other section, or 1 card will process the basic graphics, while the other do shadow rendering or whatever compliments it, and then outputs to the same monitor...
Most games on the market (not including heavy FPS)do not utilise any of the duel processing capabilities, they hardly use a standard card... you see a performance lag because of a bottle-neck on the memory or ramdac. THe speed of both the memory and ramdac makes a HUGE difference... I.E> lets say i have a nVidia 6800 LE with a memory speed of 333 mHz and a ramdac speed of 350 mHz... (for argument sake 256 mb mem) and i have a nVidia 6800 LE TDH with a mem speed of 400 and a ramdac speed of 400 same amount of mem.... the 2nd card will outperform the 1st by FAR.... purely because there is much less bottleneck...
Check the SLI speed of the card 8 x or 32 x etc... most motherboards only handle up to 8.... but that doesnt mean that getting a 32x card is a waste.... there will also be a reduced bottleneck because its designed for 4 x hhigher performance speeds, and a year from now, you probably will have a motherboard with 32 x capabilities.
