What's the difference between the two cards?

This is a REV 2.0 card. There is no big difference from the REV 1 card, probably just a PCB change or VRM change or fan change or whatever (it is a small change anyway). Because they are at the same price, get the Rev 2.0 one.

Full details explained by 17seconds, Thank you!
 
Quote:
Revision 1.0, on the left, is printed on a lighter blue colored PCB, and has a smoother, rounder, and glossier WindForce 3X cooler housing. The revision 2.0 version on the right is printed on black PCB and has a less glossy fan housing. The housing is also not as smooth or rounded. We reached out to GIGABYTE for answers, and GIGABYTE's response is thus:

The only difference between them is the fan cover. Rev1.0 is plastic and Rev2.0 is metal. They both have the same exact spec. The Rev1.0 will phase out soon. So literally the only difference is in the fan cover, one being plastic, the other metal.
http://www.hardocp.com/article/2013/07/09/gigabyte_gtx_760_oc_version_video_card_review/