Sapphire usually likes to give a little love HSF wise and Asus app wise. Both are very good all around, so get the cheaper one IMO. Tweaking tools are very universal among a line of cards, but Asus has his own tools, btw.
I suppose another fact to consider would also be aftersales support. Depending on where you are in the world, after sales could be instant to non-existent. You'd have to check with local retailers/distributors for that though. And it's also brand loyalty at the end of the day. I've got Sapphire stickers all around the house =)