Air handlers and furnaces aren't often used side by side in Austin. If you use a furnace, you most likely don't need to consider an air handler.
Air handlers are frequently used with heat pumps and deliver airflow across your home. Some models also offer extra heating and cooling components to assist the heat pump.
A furnace works differently by blowing heated air into your vents, which circulate it around your home. As furnaces depend on combustion chambers to produce heat, they don't use some of the components you'll spot in a standard air handler.