Once you get over 90%, you produce condensate, and this is same reason why you won't find any high efficiency gas package units.
When we move in a couple of months, the last system I'm replacing at the end of this month is a dual fuel heat pump with an 80% gas furnace, as there is a 80% gas furnace in the attic already, and I'm fine with it being I use the heat pump for heating down to about 30F outside air temp. That said, the one system in the basement is a dual fuel system using a 92% gas furnace.
Any HVAC system will produce water, the question becomes where (indoor / outdoor) and when (summer / winter).
Generally most guys in NC when dealing with an attic installation prefer to reduce the amount of potential water being produced and go with a non condensing gas gas furnace (80%).
Heating and air conditioning can be very regional on what type of HVAC systems are used given the weather and how the homes are built (I promise you that you'll find more swamp coolers in NM vs NC
).
Then you also have cost of equipment and cost of installation along with how you're going to vent the equipment given the current layout (to help reduce costs). For this reason, although the majority of gas furnaces being sold are 90% or higher, you'll find that most oil furnaces along with boilers being sold and installed are in the 80% range and not 90% or higher.
The bigger issue in HVAC is that California is the largest market for HVAC manufacturers, and when California passes a law dictating what kind of equipment can and can't be used, HVAC manufacturers have to comply if they want that market share, and for better or worse, they do.
This is exactly why manufacturers produce and sell low NOx gas furnaces.
