Variety is definitely more for my sake. I enjoy watching how all my fish feed differently.
I'm currently doing frozen brine shrimp, frozen blood worms, and pellets for my pearly occelatus. I have some Ken's flake coming that has brine shrimp as the main protein source so I can stop buying the more expensive frozen stuff and just save that for a treat (I usually spoon just a few in at a time so it is more of an involved process which is fun).
My mbuna go absolutely nuts for crisps. Several of them attempt to horde the crisps in their mouth and then they get run down by other fish and their crisps get stolen. Its like fish bumper cars.