DriverHeaven posted a comparison review on the Asus GTX 280 TOP vs. XFX GTX 280 XXX. Here's a bit:

The Asus version of the Geforce GTX 280 is not going to win any accolades for aesthetics or packaging. It also struggles a little in terms of a competitive bundle, something which is quite a surprise for an Asus product but the hardware itself is excellent. Throughout our testing the ENGTX280 TOP provided results which were far in excess of non GTX 280 products and it was able to perform at an almost identical level to the more expensive XFX XXX model. This really is an occasion where price, extras and performance really need to be taken into account and while the Asus card looses out on bundled extras the price and performance mixed with a 3-Year warranty make this a very attractive option.

As always XFX have produced a card which looks great and performs even better. During our testing the XXX was always top of the performance charts and still had a little headroom for overclocking of the core. As with the Asus card the excellent framerates did come at the cost of high temperatures and fan speeds, however the design of Nvidia's cooler is excellent and noise levels never became unbearable. The bundle provided is also very good and Assassins Creed adds value to the package but considering this card has a premium price we would expect it to arrive with a HDMI dongle. XFX have one of the best support structures available to graphics card consumers and this includes a live help service, accessible through the XFX website, which allows end users to chat to a support representative in real time. Should this support option be unable to resolve the problem then there is a 2-year warranty on this product.