and I would offer that the first thing you need to consider is the truck you are going to be using this with, it's capacity, and the rules/laws about size (overall length of the trailer or truck is naturally extended with a truck mounted unit added) and weight. not every truck mounted unit can be hauled on every truck. I also agree fully with all the brands mentions, and would also consider a spyder brand, as the quality and ability to repair quickly and cost effectively is almost as important as a heavy duty frame* and the extra weight that comes with the previously mentioned brands.
* after an accident at highway speeds, it doesn't really make much difference how "heavy duty" the machine is except that the heavy duty frame is harder and more expensive to fix