As Media is a smaller subject area with less teachers in general, it'd greatly improve your prospects of getting work as a casual relief teacher (CRT) – there's less people available to cover smaller subject areas, at least if my school's attempts at finding regular CRT is anything to go by.
That said, the Media jobs that go up are hotly contested, as there's less of them. A lot of hopeful Media teachers end up teaching a second method at their school before trying to introduce the subject via a younger years elective.
Source: pure anecdote, Media's one of my methods.
It's a fun subject, but it take a lot of work to build a successful program. It's more like PE in that can require a lot of resource management, group coordination, and the pressure to take on extra duties outside of class (school photographer for any school event, come on down...). It's an art subject, but it won't prepare you to teach other art subjects well.
On the other hand, there's more VCE History students (and hence jobs) across the state, and there's skills in teaching senior history that you probably won't get in a broader Humanities method, so this might be more useful if you'd like a longer contract ASAP.
