I have the same Tuffy Deck as Overlander (but I have it in my 4 door). It's very secure, sturdy and strong, and you shouldn't have to worry about putting anything on top of it. I've even heard of people strapping an ARB fridge on top of it with other gear and not having any problems. It will look like a lot of parts when you open the box, but installation isn't hard at all. Just bolts right in. It took a friend and I less than an hour, and you could easily do it on your own. Also, you can take the deck and the rear panel out quick and easy without tools if you need to, with just the brackets left attached at the sides. The only real downside is the cost... it wasn't cheap!
The one mudmobeeler has is just as secure, it's just not as strong and I don't think it was intended to have things on top of it. It also doesn't flip up, but to be honest I don't lift mine up very often anyway. If all you need is to keep sticky fingers off the gear in the back of your Jeep, it's looks like a good choice.