This post explains that ~/.bash_profile is used for login shells, while ~/.bashrc is used for other interactive shells. Here's a useful video as well, which gives the example of some printer settings as something you might want on a login shell. In the end, it really doesn't matter too much, it's just a semantics thing. Plus, as the article says:
... the point is generally moot because most people edit the files so one calls the other anyway.