Sapphire is a well known and very reliable card. If the prices are similar I'd storngly recomend going with them. I haven't had a single one of their cards fail, my sister is even still using my old 3870 and my dad is using my 1950xt.
But which one is better ^^? There's FLEX in shop available, but Vapor-X is not. Better to wait for Vapor-X or just buy FLEX and pwn noobs?