Final answer:
dBi is the measurement that should be used to compare gain between possible antenna options.
Step-by-step explanation:
The measurement that should be used to compare gain between possible antenna options is dBi, which stands for decibels isotropic. dBi is a unit that measures the relative gain of an antenna compared to an isotropic radiator, which is an imaginary antenna that radiates equally in all directions. It is commonly used to compare the performance of different antennas.