There are several different manufacturers of exhaust brakes for the Dodge/Cummins trucks. Some brakes mount at the turbo, and some mount downstream from it. The type you choose is up to you, but I would think the turbo mount is the most popular. It is the easiest to install, wire, and plumb. Also it is protected from the harsh environment of under the truck. On the newer trucks they do not have a factory vacuum pump, which is used to operate the butterfly valve on the exhaust brakes. So newer trucks wanting the benefits of the exhaust brake, will have to pay more because there kits will include the necessary pumps and hardware needed to run the system.
I think one of the most overlooked components of a proper exhaust brake installation is the controller. This unit makes much more since, it locks up the torque converter and exhaust brake as a unit. Allowing the maximum amount of engine braking, with the least amount of driver effort.
I would look around and visit the different manufacturers web sites, call or E-mail questions, and get familiar with the product. Only then would you be able to compare and appreciate the many different brands and types of brakes.