Based on advice on this board and some other research, I had decided that a Honeywell IAQ thermostat was a good answer for my system.
Instead of installing it myself - my usual first inclination, I called a reputable service company in my area - and they carry the Honeywell thermostats.
When I called, I told the lady that I wanted the Honeywell thermostat with humidity control and I wanted to schedule a blower door test. She seemed to understand exactly what I wanted.
An appointment was scheduled, the technician comes out, and knows less about Honeywell thermostats than I do. After calling back to the shop, they decide they don't have one.
Meanwhile, the technician has taken the existing flaky thermostat off the wall, said emergency heat is not wired up, fixes that, and puts it back on the wall.
There final suggestion was for me to order whatever thermostat I want, and once I got it in, I could schedule another service call to get it installed.
Then, they charge me a service call for this visit to hook up the emergency heat to a thermostat that doesn't work right and they know I am going to replace anyway.
Lets just say that I am less than impressed.
So, which Honeywell thermostat do I want to buy.
It needs to work with a single stage heat pump with backup heat and variable speed air handler - and I want dehumidify control.
Honeywell YTH9421C1002 Vision Pro IAQ Total Home Comfort System
Honeywell TH8321U1006 Vision Pro 8000,Touchscreen + dehumidifier
The two are close enough in price that is not an issue.
I understand that I lose the arm chair programming with the 3 wire version. What other differences are going to matter to me once it is installed and working?