The substrate debate will go on until the end of time. Personally I use textured ceramic tile. For me it is easy to clean, cheap, trims nails so I don't have to, and lasts forever........if you don't drop it.

I used to use play sand but to me it was tooooooo dusty and I can only imagine what it was like for my beardie. Maybe I just got the wrong stuff?

I know of folks that use crushed walnut shells and have never had a problem.

Good luck!