I do not know if the Chaos allegiance abilities are any good, but right now Chaos Dwarves can only be played in Chaos and Legion of Azgorh. By comparison, Beastmen can be played in Chaos, Beasts of Chaos, Slaanesh, Nurgle, Khorne, and Tzeentch. I am not sure how many allegiances there are in Chaos but there are three at least that Beastmen cannot be in. Chaos Warriors have as many as seven allegiances. Daemons have I think six.