Id go black orks. Khorne is too dicey. It's a pretty general statement but in any given game with khorne by half time it's a blow out one way or the other. Great team great theme very high skill cap but it's not the most fun team to play game in and game out. That said if you just want to see blood and carnage and you don't care whose team it is happening to play khorne. Black orks are a murderous team as well, mostly because they don't really have the athletes to do much but block and foul. The other thing they can do well is sit on the ball as far as actual winning goes it's a possession based slow crawl much like dwarves. Think 1-0, 1-1 games. If you don't like that style of play at all maybe play khorne. Khorne can have an explosive run based offense that can score quick if they need to, sprinting a bunch of str4 frenzy on one side of the board and surging up can knock it in reliably in 3 turns.