You didn't specify tank set up vs tub but here have been my personal experiences with a few options for either. When I just had 2 snakes in a divided 75 gallon tank I used both aspen and cypress and eventually a mixture of about 50/50 aspen/cypress. Then I switched to racks and mostly used the aspen as the purpose of the cypress was to add color to the tank and really no other reason other than humidity, which everyone said cypress held better. Can't say I actually noticed a difference in humidity between the two. With the tubs the aspen worked fine but as others noted it gets everywhere despite attempts to be very careful, I also found it quite dusty. Now I'm using packing paper that comes in 120 sheet packs for $8 bucks from Lowe's. It's basically unprinted news-paper paper. I really like it it is so much easier to open a tub see they messed and clean it. It's true that there is a chance for smell if you don't stay on top of things but I find this actually has led to me being better about my husbandry and keeping things clean and sanitary.