A good AC can easily move 3-5 watts of heat for each watt of energy it requires to operate. No such luck with heating systems, they at best get you 1 watt of heat for each watt they take.
You really need to qualify that statement. You get 1 watt of heat for each watt you use... for resistive heating. Many places that need both cooling and heating don't run an A/C and an electric heater, they run a heat pump, which pumps heat either into or out of the house. Because of the heat differential, one direction may be more efficient than the other, but it is still much better than a resistive heating element
In one minute of research, comparing a 2.5 ton 13 SEER A/C to an equivalent heat pump, the ability to both heat and cool adds a little less than %20 to the price at Home Depot. Installation costs are likely identical, as they both consist of the same components. With that cost differential, an A/C + resistive heat solution is only smart for a place that only needs heat a few nights per year.