Sapphire R9 290X vs Read XFX R9 290X? 2 graphics card same company? what's the difference?

The std cooler on the cards in your link is loud and barely sufficient! The one I posted is improved over it! But really to answer your question The GPU (processor) is made by AMD and the different partners produce the cards. First after release of a card (not counting renames like 280X) all the cards are same since they are using the AMD reference design. Later on they start popping out from the partners with their own cooling and PCB design!
 


Between the two cards you've linked to there is no difference.

The SAPPHIRE R9 290X is an AMD Reference Design card and uses exactly the same GPU and memory clock speeds so the performance of both cards should be identical.