^ it doesn't beat it in terms of fps mate agreed.
But you're looking at virtually 2-3fps lower max.
The 280 has 3gb vram,the 285 only has 2gb.
You're stuck with medium or high textures on the latest games with the 285.
The 280 will let you run ultra textures & also use the optional hi-res texture packs on new games like shadow of mordor.
Its a tradeoff but I think its worth it.