I believe the AprilAire 700 series has an outdoor sensor to control the unit. On the other I've been told stats like some in the WR line can provide the control. The only possible downside I've been told with the outside control is that it's possible to over humidify the house increasing the chance of mold.
What is everyone's choice here - inside or outside control?
BTW, this is being installed as part of a complete system upgrade (furnace, heat pump, AC, new stat etc.)