Matt087_48 :
Passmark.com 3d mark on 750 is around 100 points higher than the average 650ti . 750 only uses 55 watts, 650 ti uses 110 watts. Both are in the same price range unless you find the 650ti used on ebay. So with this being said the 750 is the flatout winner of these two.
passmark is not a reliable source. Nor is any other score based synthetic benchmark. You should be looking at only game benchmarks.
The 650Ti is stronger than the 750. But not very much.
If you have a powerful 500/550W power supply, go for the 650 Ti. Otherwise go for the 750.
However, if you're looking at performance/watt, then the 750 wins, hands down.