I heard r9 390 MSI cards OC the best and have the highest hashrate/stability, the RX series MSI suck ? About gigabyte, I bought 3years ago 3x r9 280x gigabyte and 5x asus dc2t, all of the gigabyte still run, after almost 24/7 3 years and 4 of the asus died within a year, all had fan failures withing 6months but 1 simply can't display anything, crashes during driver load. So in my opinion, gigabyte is pretty good, it's usually the cheapest card and maybe I've been lucky but they are quite durable, right now they are on zec mining with 380hour+ uptime. All I know, avoid asus, it's pretty easy now that they are priced the highest tho