The advantage of a short story is that it is an amazing type of fiction when one needs to hurry. It is considerably short, which is a strength in one way. On the other hand, that is also its' weakness. When one wants to pass time reading, a short story is a horrible choice. You'd probably be done with it in under 10 minutes.
A novella is basically perfect for some people. It is shorter than a novel and longer tan a short story. It is perfect for reading when you have a break from work, homework and many other things. But, a novella can be disappointing. It can be 100 pages, and if it is a side story from one of your favorite book(s), it is definitely disappointing.
Finally, the novel. A novel is wonderful for passing time when you're bored. It's wonderfully long length is paradise for big readers. However, for people that don't like reading much, it is not a 'wonderfully long length'.
Really, it depends on whether or not you have little time, a break or if you are a big reader to decide between a novel, novella and short story.
