So I got a special promotional deal with Blockbuster and now I'm wondering which one to keep as there is no point in me paying rental for two different places.

Which one would you reccomend? Ideally I'm after anime titles. That would be the crux of my decision.

Blockbuster discs actually work

Have you used both side by side? If so, I'd say that's a great opportunity to identify the company with the best selection and fastest delivery time.

Therefore, I'd go with whichever company provided the better service.