First, let’s see how large the gap is between the GeForce GTX 680 2GB at its default 1006/6008 MHz and the GeForce GTX 670 2GB at 915/6008 MHz:
The senior model isn’t much faster. Interestingly, it enjoys a larger advantage at 1920x1080 where the GeForce GTX 680 is an average 7-8% faster across all the tests. When we switch to 2560x1600 and the graphics memory bandwidth becomes a more important factor, the two cards differ less, by only 6-7% on average, just because they have the same memory bandwidth. Considering that the GeForce GTX 680 is 25% more expensive in terms of the recommended price, the few extra percent of performance doesn’t seem to be worth the $100 difference.
Moreover, when slightly overclocked to 1070/7028 MHz, the GeForce GTX 670 turns out to be faster than the GeForce GTX 680:
The overclocked GTX 670 only fails to overtake the GeForce GTX in one test mode of Hard Reset and in Total War: Shogun 2. The average advantage of the overclocked GeForce GTX 670 over the default GTX 680 is 4-7% at 1920x1080 and 5-8% at 2560x1600.
And now let’s compare the GeForce GTX 670 2GB and the Radeon HD 7950 3GB at their default clock rates because their recommended (and retail) prices are identical, the Radeon's results serving as the baseline.
Save for winning Sid Meier's Civilization V and Total War: Shogun 2 in the antialiasing mode and delivering the same performance as its opponent in Metro 2033: The Last Refuge and the high-quality mode of Aliens vs. Predator (2010), the Radeon HD 7950 is inferior to the GeForce GTX 670. The latter is an average 20-29% faster at 1920x1080 and 19-32% faster at 2560x1600. By the way, the difference between the GeForce GTX 680 and Radeon HD 7970 was smaller in our earlier tests.
Now the final pair of summary diagrams helps us see the difference between the GeForce GTX 670 and GeForce GTX 560 Ti 448. Ideally, the new card should have been compared with the GeForce GTX 570 but we didn’t have the latter at hand during our tests. The GeForce 560 Ti 448 is in fact close to the GTX 570 in performance, so this comparison makes sense:
The GeForce GTX 670 is 43-45% faster than the GeForce GTX 560 Ti 448 at 1920x1080. The gap grows to 50-55% at 2560x1600. That’s good but the GTX 560 Ti 448 is about $110 cheaper than the GTX 670 (and the GTX 570, oddly enough, costs another $10-20 less).