Get the sapphire, the warranty is good, but you will probably have to use it is the problem. Sapphire is just about unbeatable in AMD. Much better quality and cooling. Anything over a 7700 series card from XFX tends to run hot as well.
The XFX card is just slightly faster 1-3% (nothing a manual OC can match) The Sapphire cards is 50$ cheaper and has somewhat better cooling, I would get it instead.