Adjust temperature separately:

Whether have you ever experienced too hot at upper floor and freeze at lower floor when using Air Condition in summer, and too cold at upper floor but hot in lower floor when using furnace in winter. To solve this problem, there two A/C and two furnaces installed in this house, make you can adjust temperature separately.

Energy saving:

You can turn off one, just use anthor one you need. consume less energy to reach the temperature you want.