...As you've seen from the responses so far, this subject will get you lots of different answers, almost all of which will be recommending the brand, type that each person owns. Just the way it is with subjects like this. :)
Since you have a DP with full air brakes, I would agree that Air Force One (or maybe M&G) is probably the best choice. That is, assuming money is no object and you want the absolute best you can get regardless of cost.
However, for most of us, money IS an object/factor, and must be considered. If you want the absolute best you can get for the $$ involved, bar none, get you a Readybrake, like already mentioned. Costs several hundred $ less than anything else, and gives you a very simple, easy to install and maintain system that works great.