WordPress: WP_User_Query vs get_users?

I've got a quick question. Can someome explain the difference between these two functions? Well, I guess that's the answer, is that one is a function and one is a query class, but I'm curious what sort of performance differences there might be or why you'd want to use one or the other.

The docs for both WP_User_Query and get_users look similiar, some I just wanted to hear from some other developers...