Air handlers and furnaces aren't often installed side by side in Savannah. If you rely on a furnace, you probably shouldn’t need to consider an air handler.
Air handlers are often used with heat pumps and manage airflow across your house. Some units also offer secondary heating and cooling parts to assist the heat pump.
A furnace heats in a different way by pushing hot air into your vents, which move it throughout your residence. Since furnaces rely on combustion chambers to make hot air, they don't have some of the pieces you'll find in a standard air handler.