I have been using newspaper for substate for quite a long time, and will continue to do so for the forseeable future. When the babies are in del cups, I use liners that are actually coffee filters as the substrate.
An adult corn snake ingesting bits of aspen bedding will normally not cause a problem. A baby, however, may find it a fatal mistake. I have heard of it happening enough times that I do not consider the risk to be worth it. Take a look at a bit of aspen bedding in your hand and tell me YOU would like that going down your esophagus.
Aspen is also rather dusty and the dust particles could irritate the nostrils of the small snakes. Also, if the aspen is dry, it can somewhat dessicate a small snake that is in constant contact with it. If the aspen is wet, it can promote the growth of bacteria and give insects a welcome environment to set up a home and mutiply rapidly.
Newspaper, when used and the snake stays on top of it, can be simply bundled up and thrown away. The cage is clean. With shavings, if you spot clean, you leave residue on the bottom of the cage. Eventually the smell will drive you to do a complete cleaning, and you have to break out a scraper to do a complete job of it at that time.
If you are resourceful enough, you can get newspaper for free even in large quantities. I know of no free source of aspen, even in small quantities.
So all in all, after, let's see, going on 25 years using newspaper, I have no complaints about using it and absolutely no reason to even consider changing to anything else.