It's all a matter of preference for you. I have tried paper, shredded aspen and even sani-chips.

- Paper gets messy quick and doesn't hold odor
- Shredded aspen was great but was just very dusty and drove me crazy
- Sani-chips doesn't hold liquid as well as the shredded aspen but is dust free. It's also a bit messy cus it's so fine but again I love it because it looks nice, and has a nice smell.