I like the bowl type better. We use rotating barrels and a vibratory bowl type. For a nice polished surface on aluminum, you will need to rough and finish tumble it. We use a plastic type of media for the rough tumbling. It leaves a soft, matte surface. It's a good surface to anodize. For a bright polished finish, ball burnishing is the best. We send a number of parts out for this process. There are some hard, ceramic media types that will put a nice finish on aluminum, but not as good as ball burnishing does. It approaches a hand buffed finish.