I painted a couple of different bikes back in the day. At the time, all I had access to was enamel in spray cans. While color selection is pretty good, and they're easy to use, the durability of spray enamel is not good at all. It didn't take long before my paint jobs looked pretty beat up. Powder coating works well, but you have to be careful with aluminum. Some powders require fairly high curing temperatures, which can anneal the aluminum. Also, while epoxy, whether appliance spray paint or powdercoat, is tougher than enamel, it is not resistant to UV. It will oxidize and become chalky over time.

If I were going to paint a frame now, I'd use a catalyzed automotive enamel from an auto body supply. It's a good bit more expensive than what you would get at a home center, but will last much longer. Color selection is essentially infinite, with metallics, pearls, and lots of other options available. Some places can put the paint into an aerosol can, if you don't have a spray rig.