In general, it is better to have as variety of text types. I don't remember the exact wording of the syllabus, but there is something in there about having read/analyse/appreciate the wide range of text types.
Of course, if you think that you can only find two novels/films etc that are able to more strongly support your belonging thesis then I would use them instead of making your argument(s) weaker just so you can incorporate two text types.