How can you tell if a cat is dominant?

I got two male neutered 2 Weeks ago.They are now15 weeks old. one is black and white and the other is tabby and white. The black one is quite a bit smaller than the tabby( when we went to the vets he was 1.57 and the tabby was 1.81) but I think the smaller one is dominant. How can I tell? the black comes and snuggles up to the tabby and licks and preens him.Neither moves out of the way when we put food out and the black one always plays with toys first, but I think that's because the tabby is lazy.