If you could put them into the same spot recording the same thing from the same distance that might be a good way too tell how close they are matched. Of course that wont account for differences in tone that the individual mic could have.
Maybe you could take a play a 1khz tone through a speaker and close mic it from say 1 foot. Then put the same mic through the EXACT same test. Which would be tough but achievable. Then run that through a frequency analysis and maybe you could get some idea from how close the graphs match? Not to mention that you would have your ears to tell you how closely they matched.
All this can be done with Cool Edit Pro
Poor mans anylysis? Maybe? Maybe it won't tell you anything. But I think it will tell you more than you know now.
Beezoboy