Hey, I'm not in the marine cadets, I'm in the CCF. Each contingent is affiliated to a unit, and I'm in the army section, and we're affiliated to the Blues and Royals.
cadet units that I've come across have been very variable. From what I've seen, and what we've been told by serving members of the forces, mine is one of the best I've come across fortunately! However, all the Marine cadet units I've come across have been up with a high standard. I have yet to come across a marines cadet unit that is at a low standard. there are individuals, of course, but as a whole, the units are good.
As for preparation for training, I think they are very good, because the camps and exposure to military life will give you a bit less of a lifestyle change/shock, however we also need to keep in mind that none of what we've done is anywhere near enough for us to be confident in our abilities! I've used the SA80 and LSW before, but that does NOT mean I am up to anywhere near good enough standard!