Out of the 2 brands Asus will come on top of a Zotac card. I would personally recommend the EVGA GTX 970, have never had any problems with an EVGA card and have always lasted atleast 3-4 years before I've upgraded them.
I have two Zotac 970's and I don't see what the problem with the brand is and until I see some actual evidence of problems I'll put the lack of recommendations down to pure snobbery.