I don't know much but it is switches between hi and low output making droplets of spray transfer instead of continuous spray transfer. I have heard it is stronger welds too. Exactly why it would be chosen over a different process is beyond me though, never done it. It sure looks good though...like tig. I do know that when it switches to low output it keeps the arc but does not allow metal to be put down.
I am sure someone else can give you a better explanation than me. I am just a nurse lol.
And I think the only reason you would need it unless you are a fabrication shop is to have it. Just like I bought a 212 instead of a 211 because as you said bigger is better haha. I have a diesel and only pull a trailer every once in a while, someone asked me what I was going to pull with that truck and I said anything I damn well please! Get what you want because no matter if you really need it or not your going say if I only would have got that then.