Chuck,
Our 2000 Marquis had the Hurricane while our 2001 and 2007 Contessas had Hydro Hots (same Co system as Aqua Hot). Not sure why SMC switched to AH in 2001. Currently AH appears to dominate the RV market but ITR has a competitive product, Oasis that is found in some RV models and is also used in the marine industry as is AH.
We had the Hurricane from 2013-2015 and the following is based on my memory so if current owners find my memory faulty, please correct me. The Hurricane utilized a hot water tank that was prone to fail at some point as RV owners are at the mercy of parks to fill water, thus have little control of the water quality which can lead to tank leaks. Also the Hurricane had winter and summer valves, hidden away under the bedroom engine access panel whereas AH didn't need them. The Hurricane was subject to air locks if you when you drained and then refilled it. I found them a pain to resolve. On the plus side I found their tech support super. I also seem to remember that the operating system was a bit more "complex" than the AH as you had to remember to have a switch in the bay turned on to activate the interior controls.
The HH we had from 2005-2012 was not trouble free either. The mixing valve failed, the fluid tank radiator cap was much larger than a std radiator cap and finding a replacement was problematic. A check valve above one of the stir pumps failed.
The HH we had from 2015 to 2024 was fairly trouble free. However I think that was due, in large part, to the use of heat pumps for normal heating. Thus we very seldom used the diesel boiler in the HH but rather the electric heating element. We also found that while on the road, the engine to HH heat exchanger kept the water hot enough even over night (unless we were showering) so we did not have to have the electric HH element on. That cut down on the maint (no need to change the diesel nozzle annually, etc.). However I would recommend changing the fuel filter at a regular interval to prevent the fuel geling.
Overall based on my experience, the AQ/HH units would be my choice, but both units will bite you if you don't maintain them. If I were ordering a new RV with a choice of Oasis or AQ, I'd look very closely at the Oasis unit though.
Sorry for the long story.
Steve
