both are great motherboards, but I prefer the ASRock Z87 Killer, as I know two people who own and and recommended it to many people, they are also very happy with it.
If your case scheme comes into account, get the board that looks best in your case, both won't disappoint.
You won't go wrong with both put in mind the z87 extreme 4 it's absolute best for the price range
I got the fatality killer but i kinda want the extreme 4 now i love asrock and their support service.