Just over 2 years ago I had a demo of both the Host and Envirodri, at different times but on the same carpets.
They performed very similarly, so much so I simply chose the cheapest, by far, which was the Envirodri.
The Host did have benefits in as much you could add a vacuum pod. This means you could agitate the carpet when dry and release all the bits and suck up at the same time. If you dont have the vac pod you have to go over with a vac cleaner - double the effort (but still worthwhile).
Point to note is that a set of brushes (2) are usually included with a machine but there are different grades for differring tasks ie black is for hard floors, gold is for wool and 3 more inbetween.
A set for Envirodri is about £95, a set for Host is about £170.
The Host offer of £999 inc a set of your choice. It was a limited offer so check it out, and this new machine is not capable of having a vac pod fitted at a later date.