GTX 670 Advantages:
6% faster
GTX 760 Advantages:
Newer Architecture
Built in h.264 encoder (faster performance than GTX 670 when using fraps or other recording tools)
Cheaper by $10
700 series sounds better
Verdict: I'd go with the GTX 760 primarily because it sounds better. When someone asks you what your video card is, it will sound better saying that you have a GTX 760 rather than a GTX 670. It's just my opinion, but anyway, my vote goes for the GTX 760.