I have had two Hydra Master
Cds.
The machines are very dependable and hardly ever have a problem. I think
Butler is the same (no personal experience with a
butler though) These are very simple, dependable hardy machines.
The heat depends on the package you are getting (Salasa etc.) and you need to decide if you subscribe to the crazy, burn your butt off, HEAT camp or not. I don't. You will get more heat from some of the slide ins and definitely from the machines that utilize a propane heater.
However, my next machine is going to be a slide in.
With both machines my problems were not the machines but the Fords engines and also the transmissions. Yes, I maintained the engines religiously. My mechanic, and he is top notch, swears that none of these van's engines is designed to stay in idle that long. Also, if you go back about 8-10 years, you can tell what Ford (I don't know if it is Ford specific) thinks, as years ago they stopped approving power take off machines in their vans (voided the warranty.) They did allow it back later, but you wonder if it was more due to the large market, not just carpet cleaners, ambulances etc, than what was actually good for the engine and transmission.
The power take offs (like the
CDS) are more employee proof and require less maintenance and mechanical know how, if you intend to service it yourself.
No matter what you decide, you can't go wrong with either a
Cds (or a
butler) or any well built slide in. In general, the less complicated they are the less can go wrong.
Hope this helps and good luck.