Do most people use the single stage (heat or cool) or the dual stage (heat and cool) controllers?
It really depends on ambient temp where you ferment.
If you have ferment fridge in the garage and temp swings wildly then get two stage controller.
If you ferment in basement where there is quite moderate temperature you could get by single stage.
I use dual stage Ranco controller and I ferment in the basement.
My ambient basement temp is 53F.
When I brew lager I cool first week and then I raise temp 2F each day till I hit 56F - 58F.
I will have to heat there.
When I ferment Ales I would have to heat now all the time.
Johnson is a good controller but it is PIA when switching from cool to heat because you have to open the box.
With Ranco it is just in settings.
Not sure about LOVE controller.