We have had the professional version of the rug doctor for our home for a few years. It has been well used among our family. Not only does the Edic surpass the rug doctor in every way, it's not even in the same playing field! This thing holds around 12 gal, where our rug doctor only held about 2. We chose the optional heater with the EDIC so we don't have to constantly put hot water in, the heater does it for us. And let's just face it, hands down the best steam cleaner, even at home owner level for those that want professional results without calling someone every time the carpet gets stains from kids or pets.
So far it is able to do the job that I have expected The water stays hot so I don’t think the external heater is that important. I do wonder if the one with more power would do better job but 100psi seems to work well so far.