With suspending a user, you can set a time period. I believe one may be set by default. So you may have to change that. Anonymizing users removes their account in a way - removing their personal info, but changes the ownership any posts they made to an anonymous user created by the system. That way their posts/replies are still available to keep the flow of the discussions relevant.
Now I’m curious… if someone is suspended permanently, will they be automatically deleted… and if so, what happens to their posts. 
Something else I’ll have to look up. 