At school they use silos for the smaller birds and I can't say I am a fan of them personally. The seed silos have to be checked a fee times a day because the birds leave a lot of empty seed hulls on top of the seeds, and end up going hungry because they can't find the seeds underneath. Their water silos really often get just as messy as the water bowls the parrots and other larger birds have... Maybe it's just the birds at school that do this, though.
I prefer the steel cups. They're easy to clean and durable. Whenever I'm not sure if Puck has eaten all of his food, I just go outside and softly blow the empty seed hulls out of the bowl. You can easily see if there is anything left that way. I get Puck a fresh bowl of his mix when he has eaten so much that the "leftovers" will not last him a full day, or when he has pooped in it and it needs to be washed.
I once dropped a bowl that was empty or almost empty to the bottom of his cage. So the hulls were all over the bottom of it. As I washed his bowl I could hear him searching on the bottom for any dropped seeds. He spent a good half hour like that, even though I had given him a fresh bowl of seeds in his cage! Silly bird