New is always better warranty wise and even OC for OC the 1070 is faster, I know GPU's hardly ever go bad but it CAN happen and has happened. To be in that situation with no recourse is a nightmare worst case scenario.
I just saw the 1070 strix ($430 w/tax) in action and that thing has a ton of performance, and very pretty if you have a clear window in your case. It never went above 60 degrees which meant no gpu fans on and nearly silent, you can also plug two case fans into the card that the card controls giving it's self additional cooling if needed (my friend only had one hooked up as he didn't want both front fans to be dedicated to his GPU only).