There is a clock difference between MSI and Zotac. (higher is better)
MSI: 1582 MHz GPU clock and 1771 MHz boost clock.
Zotac: 1607 MHz GPU clock and 1797 MHz boost clock.
MSI is 279 mm long while Zotac is 300 mm. (21 mm longer than MSI)
Rendering power is slightly better on Zotac than on MSI.
I hope I answered your question.
P.S. Whatever you decide you wont make a mistake.