OpenGL is a feature of the chip and both should be 4.2.
Can't tell you which will be " cooler,safer,long lasted and quiter" since you didn't link or give a model number
Sapphire is an AMD partner, and I have had good experiences with their cards and RMA department (not the cards fault, there was a cat involved).
Never cared for gigabyte or xfx. But all 3 are fine, whatever is cheaper. Paying for an overclock is a waste when you can do it yourself, but your call