Anyone know any difference between Grad Diploma of Teaching, and getting a Masters of teaching?

Im a Graphic designer who went through uni and did Honours, and im getting pretty sick of my work, and ive always had a love/knack for teaching, so im looking to do some kind of postgrad study to get into secondary teaching. Newcastle uni (my local uni) is offering a diploma that they say will let me do that, that i can do in a year, or theres obviously the masters, which they have as a year and a half.

Is there much difference between the two once its all said and done and, more importantly, is the masters worth the extra six months of study time?

Ive inquired through the uni, but before they get back to me I'd live to hear some opinions that arent filtered through the lens of "we gotta sign this guy up to get the uni more money"