Forgot one - 15" Numatic rotary.
Favourite - difficult to say cause they are for different ie hwe, rotary, encap, crb
Easiest to use is defo the Cimex C48. I would love to be able to try the US fluids like ReleaseIt, but not available over here - frustrating cause I have seen some amazing results.
For overall best results - got to be hwe, therefore the Prowler and the Scorpion.
The Prowler is the best of those two, BUT if I mounted the Scorpion in the van, like some have, complete with auto fill and auto dump I think that would do much more then a very satisfactory job.
but like all things, the machine is just part of the sum, you definitely need the right cleaning fluids.
Up to recently I have been using Nemesis a lot, with Powerburst on really bad ones. However, like a lot of cleaners, more recently I have been using Fusion8 more and more, with HD when grotty. Waiting for a delivery of Solu-boost to add to the Fusion8 on grott ones.