Didn't want to start a new thread for this, and this fits the topic well enough, so here goes.

I'm playing CoD4 right now, and was wondering which would give better quality/performance?

1280x1024, no FSAA.
1024x768, 2x FSAA

From what I see, the higher resolution gave a cleaner picture, but probably lowered performance a bit, but that might be just me. I have no idea what load AA has on the card. 1280x1024 has 1.667 times the pixels, so I'll assume 1.667 times the load.