I use paper towel.
I check my tubs twice a day and it makes cleanup much easier for me. I used to use Aspen chips but the brand I was using contained mites. These were NOT snake mites, but were crawling all over the snakes since they were in the bedding. I will use Aspen shavings (different brand/different source) when I want to increase the humidity. What you use will depend on your environment, and your own since of appeal. I personally wouldn’t use the eco-earth for Ball Pythons. I fear that it may stay too wet/damp and may cause scale rot. I like my substrate to be dry or (in the case with the aspen shavings) provide air circulation under the snake.