I have one, and looked at the same choices you are looking at. The Vapor Chief seemed to give a good combination of quality and performance for the money. I'm not sure why there is so little discussion on them.
Give them a call. The owner (Kevin) is very willing to answer any and all questions you might have about the guts of the machine. The current models are designed around all he has learned about the quality of various internal parts through several generations of machines.
He is a detailer by trade and says he was one of the first US detailers to adopt vapor steamers. Also, he stocks all the parts if anything ever needs fixing, and he is willing to just send you parts so you can fix it if you'd prefer, as opposed to having to pay shipping for the whole unit and wait for a fix and return shipping.