Actually, ARE is the best. (Just look at the back of my truck!) Snug-Top makes good shells, too. (It's the one my Dad has.) Both are also expensive, like Leer.
As with many things, you do get what you pay for. All these brands are well constructed (strong) and will hold up to the rigors of medium-harsh wheeling. Style factors into the cost - the "better" it looks, the more it costs.
The bigger companies build a shell for your truck - specifically your truck. They have individual molds, and match the paint to your factory paint.