The bed-a-beast is made from coconut husk, so it's probably cleaner. That's what I used for the small baby when I first got him last year, but for the indoor adult, that someone found wondering around, I use the potting soil/sand mixture because I can make a larger batch, so her quarters has substrate deep enough for her to bury herself completely in it. Plus, the more substrate I use the slower it dries out and less I have to water. That's I use the sand/soil mixture because they are so cheap....