That question is dependent on some factors, like ambient air temps, the air flow in you case and what sort of details/taxation you have on your GPU(any overclocks). Each company will have their own marketing team tout why their card is better and which is cooler but at the end of the day, they are near each other by a few degrees, like 2-4 Deg C. There are cases in the market that can allow you to slap on 12 fans (give or take) but they don't do squat for improving airflow or heat dissipation.
What I'm asking for, is a list of your current specs like so:
CPU:
Motherboard:
Ram:
SSD/HDD:
GPU:
PSU:
Chassis:
OS:
How old is your PSU?
Both cards are good regardless of which one you pick.