How can you tell a good spatial microphone from a not-so-good one?
The simplest way is to look at the decoded virtual microphone polar pattern graphs. If you decode a microphone’s spatial recordings to, for example, a virtual mono cardioid, how good are its polar patterns? How deep is its rear null? 20 dB? 30 dB? 40 dB? How consistent are the patterns over frequency and angle? At what frequency does the polar pattern start to break down? How quickly and how badly does it break down?
Look at some other polar patterns, including higher-order polar patterns. See if the performance holds up or not.
Some spatial microphones are as good or better than the world’s finest mono microphones. Some are not.