Variety is the spice of life.
Flake foods are very convenient, and there is a large selection out there. The better brands will suggest what species the food is targeted for. Buy the smaller containers, and alternate between a couple different kinds, and replace with a different kind when you run out.
Live foods can be very interesting to watch the fish eat, but have a high chance of carrying bad bacteria or parasites. If you want to try high-protein foods, the frozen and freeze dried ones are good.