I don't think the more expensive ones are any better than the cheaper ones. I think you're just paying for the name. I might be getting these two mixed up, but I think Dasani is made my Coke and Aquafini is made by Pepsi. There was a TV special on bottled water, and I remember them saying that one of the more expensive ones actually comes from the Detroit River, and they purify it.
By the way, in what way did you mean that distilled water is bad?