I use forest floor for the tank I keep my pied in, but I live in a really dry area. Even when I put a fresh layer down the humidity never goes above 70%. Humidity in my room is usually 20-40% and it's even drier outside. So I started using cypress specifically got to help with humidity issues.
Aspen is clean, dry, and asthetically pleasing if you're looking for a drier mulch. I use it for my colubrids, used to use it with my ball pythons too before I switched them over to cypress.