There is no best antenna. It is as the best rope. It depends on what your needs are.
Have never seen a radio and its antenna which not is measurable by a VNA.
With a VNA can radio TX and RX circuit impedance be measured so it can be matched against antenna impedance for optimal transferring of power in both directions.
An assumed high efficiency antenna can be rather useless if not matched against actual radio impedance.
Assuming impedance matching not is a problem can comparing different antenna radiation pattern be done.
Assume a fixed transmitter at distance.
Most radio chips can read received signal level, RSSI.
Comparing different antennas, all equal well matched to actual radio, can be done by reading RSSI-value for each antenna.
Result will show which antenna that works best for actual local environment and resulting directivity pattern.
There exist a lot of single chip RF receivers and RF detectors or even simple
diode detectors connected to a simple voltmeter which can be used to measure amount of power received by an antenna, when it is impedance matched to actual measurement circuit.
It will not tell if result will be same when connected to another receiver then what is used for measurement, as well as if connected to another antenna.
Especially when antenna and ground are much less in size then actual wave-length or with antenna placed internal in an enclosure, can even minor changes in antenna near field have big impact on antenna received signal level and usable bandwidth. Antenna that performed good in free space can behave very poor in a limited space.