Honestly, from an investment side of things, purchasing seems like a good idea. I know it is only three years, but the real estate market, from what I have noticed (I live in Kingston) has been fairly stable in terms of housing prices. Also, if you own where you currently are, the military is really good about assisting in selling, paying for commission, and all that fun expense that goes with purchasing. And someone might be able to speak further to this, but coming from out of province, we were supposed to pay a "land transfer tax" for the first time we purchased here; however, because it was a posting move, the military covered the cost of that. If you end up being here longer, or which to purchase a home (the military does allot some time for you to buy a home after posting I THINK-look that up for sure) you might not be able to access the benefits you are given allowance to initially. Another thing to watch out for that we were shocked by- the municipal taxes here are quite high. It was a little bit of a shock to the system.
That being said, I have heard that the Q's are nice, the rent is fair, and they are located near the water, which is a nice benefit. There are lots of parks on base, dog parks nearby, services close at hand. If you have an other half that plans on working, it might be a little bit of a drive for them, as the base is on the edge of town, and there is only one bridge that allows access to the downtown area. (I have heard that traffic sucks there) I hope that this helps! Good luck!