Are you going to dive locally? If so, the big advantage of a backplate is that it moves weight up onto your back, which means less weight on a belt or in pockets, and also makes it easier to stay horizontal in the water.
I wholeheartedly agree with Ronbeau. The most important thing about a BC is that it fits you well, and that you are comfortable using it. I do not know the Mares Dragon, but there may be nothing wrong with it at all.
The things I've seen in BCs that are worth watching out for: If you buy something with weight integration, make sure the system that retains the weights is both easy to jettison AND difficult to lose unintentionally. Velcro retention systems will age and become insecure in a fairly short time. Systems like the DUI Weight & Trim are fairly secure, but a bit of PITA to rethread if the weights are pulled.
I like something with two cambands. Not only does that hold the tank straighter on your back, you have a bit of insurance if you happen not to tighten one camband adequately.
Many BCs have pockets, but it's often true that they are either too small to hold much of anything, or too difficult to access when in the water to be useful.
Look at the placement of the dump valves. Remember that you have to get the air to them to dump it. If the valve is in a place where you are going to have to assume an unusual attitude to get the air there, it's not going to be very useful.
I don't like pull dumps. Repeatedly pulling on my inflator hose just seems like a bad idea to me. They're all made of plastic, and plastic fatigues and eventually cracks and fails. I don't want to pull the inflator hose off my BC (and this happens!) Of course, you don't HAVE to use them, but why pay for something you don't want?
Finally, realize that what feels pretty comfortable in the shop may turn out to be sloppy and annoying underwater. Putting a tank on the BC changes the way it hangs on you, and even more, we don't (or try not to

) dive in a standing position. Going horizontal with the tank on top makes for different dynamics. For this reason, don't buy a BC where, to fit it in the shop, you are at the far end of the adjustment available anywhere, because you may find that, underwater, you need something tighter or looser than you do on land.