Sapphire has a very good track record and I personally prefer them. BUT, Gigabyte's Windforce cooling actually outperforms Sapphire's Tri-X Vapor-X cooling on this card. I've been able to easily overclock the Sapphire and I think it looks better too (I have a blue/black theme).
Tom's Hardware has a great article that compares all the top models of the R9 280X. Personally, stay away from XFX as Sapphire, ASUS, MSI and Gigabyte typically have better quality products. XFX, Colorpower and a few others are considered lower tier.