both are same if there is a difference there its very tiny but i will go with the asus because i have heard that zotac gets hotter and asus has better cooling and i personally like the red and black looks of the asus....
I would go with Asus as well. You can actually buy a separate back from them as well. Which are very sexy might I add. I've got the Asus R9 280X and they are one sexy beas!