There is nothing wrong with the Gigabyte card, personally I think it's as good a make as Asus.
Basically there is no real difference between any of the cards, they all use the same GPU and RAM (if the same size). It comes down to the board they are on and the cooler used and some manufactures will "bin" the GPUs so that their top of the line cards have better overclocking capacity. I wouldn't be worried about the card you choose vs the Asus, any difference in performance wouldn't be noticeable.