For roof mount A/C or heat pumps, Dometic, Coleman, and Atwood seem to be the big three. I went with the Coleman Mach 8, 15k BTU heat pumps. I've only had them installed for a week so can't say too much except they were relatively easy to install (with Coleman control boxes and thermostats). Details here
. There are a variety of models to choose from - A/C or heat pump, BTU, condensate pump, etc...
I had Dometic heat pumps in my last RV (40') and they worked great and were plenty powerful. That said, I never spent any time in super humid locations.
Remember that heat pumps only produce heat down to something around 40 degrees so they are not a replacement for a furnace/real heat.