However, usually it's more expensive. The 760 around 240, the 670 around 300... but you can get a 770 around 340, so if I were making the choice it would be if it was worth it to jump to the 770 rather than the 670.
Well 670 has overall better scores in all kinds of benchmarks. More CUDA cores as well, just as an example. However the 760 being a generation younger and having GPU Boost 2.0 it could be great fun overclocking it, also it has OpenGL 4.3 - but I don't suppose that matters to you . Though if you are not exactly a OC maniac I would go for the 670 - I know it is weird to go for an older one, but it will score higher FPS if thats what you are looking for.
EDIT: I also agree with Traciatim - spending just a little more would be worth the 1 generation if you can spend that kind of cash