One technique I find most useful in matching mics (this is done here for matching DSM mics) is to apply pink noise to two closely positioned mics at >1 meter distance from a speaker.
Amplify the output of the two mics and invert the signal to one of the mic channels, then sum the two channels to mono and observe the spectrum graph of this mono signal.
If the two mics are perfectly identical over the pink noise frequency, then a straight line results when viewed on a spectrum graph display. Where the sum of two mic signals (one channel inverted) are not an identical match, the summed output appears as a deviation from a straight line over the test frequencies.
If one mic has higher output than its mate, then a straight line still occurs if mics have perfect "bandwidth over frequency match," but the straight line will have some value other than 0 db indicating amount of overall output sensitivity mis-match. This sensitivity mis-match is quite OK when known and can easily be corrected with simple level adjustment of recorded channels in post edit process.
While omni mics need not be rotated for doing a test like this, directional type mics should be rotated 30, 90, 180 degrees to observe any change in off-axis response match existing.