They are both good. Here is what you need to consider to help you make the decision.
660ti is the choice if:
1. your motherboard supports SLI
2. You plan to use Nvidia 3D vision
3. You want to use the newly announced Project Shield Nvidia handheld
4. You find the GTX 660ti for a very good price
7950 is the choice if:
1. Your montherboard supports only crossfire
2. You want to use eyefinity and have more flexibility for multiple monitors
3. You find the 7950 for a great price







