Most likely the bigger unit will be cheaper to run. Even if it uses
less amps, the power consumption will be higher because the voltage is
higher. Power is volts times amps times power factor. The power
factor applies to loads with motors, like the compressor and fan
motors. The power factor should be between 0.9 and 0.95 for both
units. so all you need for comparison is the volts times amps for both
units. Ideally, you should measure that whle the units are running,
not go to the nameplate. The amp rating is the maxmum amps, not the
normal running amps. My heat pump is rated 12.0 amps, but normally
draws about 6 to 8 amps when running.

That said, if your load is 1-1/2 tons, you will need the bigger unit to
cool the space. If the bigger unit is more efficient (Hgher EER) it
could be cheaper to operate than two smaller units.

Stretch