Hi from Mpls. area Minnesota. We've had both the Aqua/Hydro Hot and the Oasis (our current unit) and we do prefer the Oasis as it is significantly quieter than the Aqua/Hydro Hot was in our previous MH. In other words the burner noise outside is much less than was the Aqua/Hydro hot and less bothersome to us and to neighbors when it needs to run. It also seems to be a much cleaner burning unit such that there is significantly less noticeable exhaust to bother neighbors in those campgrounds that pack ya close together.
Ya know, I can't recall whether our previous Aqua/Hydro Hot (an 06 model) had two heating elements or not, but our current Oasis does have two which can be convenient when ya need a little more hot water volume, although, it's seldom we have both elements on.
Hope this helps.
Steve & Lynette
2014 Newmar 3103 BAYSTAR/Triton V10 w. Banks/05 Honda Element toad