How do you use the Libraries vs the Genres feature?

[c2h6]

I'm reorganising my media collection and thinking about how to best sort my media.

I used to have just 3 libraries (Movies/TV/Documentaries), but I realise that some people sort into genres using Libraries - for example, separate libraries for "Drama", "Comedy", "Reality TV", etc.

What do you do, and why?

I thought sorting into genres using Libraries would break the way the Genres tab works, but I could be wrong.