Thanks for the comments.
Alan, you raise a very good point about 'just do both' ; that is exactly where I am at the moment and to be fair the old adage "why fix it if it ain't broke" could be applied. The issue for me is that I offer 3 methods of carpet cleaning, guaranteed to be the same price. This gives me a USP of being able to say to customers that I'll turn up with the kit to use 3 possible methods and advise on the best method for the job. It works really well as a marketing approach and customers like it - but I'm bloody sick of humping a portable HWE, the GEN4, a Numatic Rotary, an Oreck Orbiter, and all sets of chems to every job!

You're absolutely right that chem costs are higher on dry compound compared to HWE. Although I find them lowest on Bonnet cleaning (or low moisture rotary as I prefer to call it

). James - I haven't really had that problem with the compound before, although I do agree that in general, the post-clean vacuuming can be a bit hellish and long-winded when doing an Envirodri clean. I honestly can't ever say I've seen sponges left in the carpet though; and I've never had a customer calling back about left sponges. I find that if I spend as long on the GEN4,
before putting the sponges down, it pays dividends for when you're later getting them back up. If I don't use the GEN4 before putting sponges down, they are harder to get all back up.
As an aside, it does make me laugh when you watch the Host videos and they talk about how nice it is without 'the mess from water' ; all the dry compound methods are THE messiest form of cleaning carpets! The sponges can get everywhere, although with practice they can be contained. The cleaning of the GEN4 is also quite hairy; I find I need to spend 30 mins cleaning it per 3 hours of use; that's quite a lot of time.
I think ultimately, Alan is right, the best thing to do is probably to keep both sides but focus my marketing on the side I'd prefer to be working in. A Thermadry would be lovely; hardly any set up, light work, good results, fast dry, and little after-clean of the machine. It may well be my next toy on the list.

Dave.