Emergency Heat Coils vs Space Heaters
Q:  "emergency heat or electric space heaters...more efficient for short-term heating?"

A:  The efficiency is identical because they both supply heat from resistive electric heating elements.  The operating cost of the emergency heat is likely to be more expensive because they are large heaters that heat the whole house, whereas the space heaters can be used to heat only the occupied rooms.

Q:  "Is there a place on the air handlers, where the wattage for the heat coils can normally be found?"

A:  The information is not always easy to find since most fan-coil units accept a wide range of heating elements.  It is most likely on the electric heat coil unit itself, inside the fan-coil box, downstream of the refrigeration coils and the blower.  Very roughly, the emergency heat is likely about 1/2 to 2/3 the rated capacity of the heat pump.  To estimate this number in KW, divide the BTU/hr of the unit by 3412.  For example, a 48000 BTU/hr heat pump would be 48000 / 3412 = 14 KW.  An electric heater about 2/3 that size would be 10 KW.