Well, the only 2 points i'd suggest considering is:
1- The PCB of the card (some 670s are built on 680s PCB which is better). In this case i really don't know if any of the cards you mentioned has 680 PCB.
2- The cooling solution on the card. In this case, Gigabyte uses very efficient solutions on their cards and much better than PNY in noise and cooling.
Gigabyte one is actually recommended by Tom's. You can read the full article here:http://www.tomshardware.com/reviews/geforce-gtx-670-test-review,3217-16.html