Also look at Quadra's "Bigfoot" and Lippert's "Level Up". The Lippert systems seems to be the most popular OEM installed levelers while the Quadra systems seem to be found on some of the more expensive coaches.
Camping World installs HWH levelers at many locations. The others also have installers too, but it depends on where you live. If you are buying the coach from Camping World, they would naturally push HWH as that is the system they install.
The main differences are that HWH have spring returns (hydraulic going down; spring going up), while Quadra and Lippert have hydraulic down and up.
I suppose on one hand, if you lost hydraulic power, the HWH system would let you retrieve the cylinders, I have not heard a lot of issues with the others.
Most systems use a single-central pump, but Quadra has the most options, including single and 4 pump systems (one pump for each cylinder), as well as automatic, manual, and wireless systems.
I had a Quadra Bigfoot system installed in my coach back in March, partly because I liked it the best, and partly since I live 50 miles from the factory, I was able to get them installed on my coach by the factory. The Lippert operation is not much further so I could have had my system installed by them.
However the salesman I talked to was kind of a shyster, and would not give me a price for an installed system, but wanted to base it on the quote I received from Quadra. He also did not want to compare the features of his system to Quadra's.
To be fair, the salesman has nothing to do with how good the system is, but since he was representing the company, and was not very forthcoming, I did not consider them much. A year later, I am still waiting for a quote.
Maybe it's just me, but if you had a customer with cash in hand...
There are a couple of threads on this website where a couple of us have installed Quadra Bigfoot systems, so you can get some kind of idea how they work, costs, etc.
There are several different manufacturers out there, and which one you decide upon might very well have as much to do with having an available installer in your area as much as anything else. Both Quadra and Lippert are within the general Elkhart, In area (with factory installation), while HWH is in the Davenport, Iowa area (which also has factory installation).
HWH as I said, also can be installed at many Camping World locations.
Also, do some research (as you are doing) and see which manufacturer has the most experience with installing systems on your model. I do know that if installed incorrectly, these systems can damage the structural integrity of the rig. I was told by one of the manufacturers that they found cracks in the sidewalls of some rigs when the cylinders were installed in certain locations.
Here are some references:
Level Up® Towable RV Leveling*
Welcome to HWH Corporation
There is one or two other manufacturers as well, but these three are the major players in the industry.