I think the easiest way to answer these type of questions is to work out what the demands on the database will be in terms of inserts, updates and selects.
In this case how many films will they be and what rate do they need to be inserted into the database?
Probably there are not a huge number of films and most of the time will be spend getting the data and formatting it so it can be inserted into the database. Then once the data is in there it isn't going to be modified very often.
On the other hand answering queries like, which actors started in movie x or which movies has actor y stared in are going to be the main function of the database.
With your schema how would you find all the films an actor stared in? You would first have to look up the actor in the actors table to find the id. Then you have to find all the movies with that actor id. That's a bit complected as the actors are stored in a string so you would have to look at every movie row and parse the actor string.
That's much more of a worry than having to check if an actor already exists in the actors table every time a movie is added.
By way of demonstration, he emitted a batlike squeak that was indeed bothersome.
