So rocksteady is actually right about reserve MP's being more like security guards then police. That being said, it doesn't mean you don't get valuable experience if you want to go reserve being transferring to reg force.
This nice thing about being a reservist first is that you will get more field experience which will help you in the long run if you ever end up deploying. Reg force MP's don't really do any field training, and I don't think they even do a C7 shoot every year. That's why they end up having a longer predeployment training then other trades.
It's also nice to make a bit of money while you're in school. You can do your BMQ on weekends in the reserves, its hard and requires serious time management skills but at least you'd have it done by the time you're ready to go reg force. Also i know some reserve MP's who have actually been able to work full time with the reg force MP's while still in school before going Reg. They didn't get to carry guns because they were reserve but it was still great experience being on shift .
I hope this helps!
OH, one more question, if you go reg force are you planning on going officer on NCM?