I have a pedal max. Why? Because I found it online before the pedal commander. It stacks with the boost max by JMS which I also have.
Does it work? ABSOLUTELY changes the truck and does what they say it will do. The boost max made a big difference in power too. You can feel it noticibly.
In regards to the pedal commander vs pedal max?
I have only used the pedal max but I'm guessing they work on the same principle and have similar performance boosts so I would say both are a great modification.
The pedal commander has a nicer looking controller box and is a little easier to set with it's push buttons. The pedal max uses a metal knob, optional, that looks like a rheostat. I hide it under the dash.
Maybe some other folks will have more insight, but I don't think you can go wrong with either.
Guy