Both can be used as bonsai subjects, in fact even though not discussed too much in the US cherry trees of all variety, including chokecherry are classic and sometimes cherished Japanese Bonsai subjects.

The Oak can be done as well. Even though there are a few oak species that would lend them selves better to the art of Bonsai, there's not too much a difference. Just keep in mind that it would be more preferable to make a larger size bonsai when concerning oak as their leaves don't miniaturize as well as some species such as say maples. Since this tree also grows slowly I would recommend planting it in the ground outside (field growing) for at least 3-4 years if not longer, to get a decent size trunk that might otherwise take three to four times as long to happen in a pot.

Good luck
-Mike