I think this has alot to do with size of collection.

If I only had a handful of babies, papertowels.

If I have a large collection, like I do, newspaper. FREE, clean, easy, efficient.

I also believe Cypress Mulch is a much better choice than Aspen for Balls, and that is what I would use for a medium sized collection, or a manageable CLOSED collection where I would almost never have to worry about mites.