Skeptical as always... there's nothing to say that any frequency graphs you get are actually from your specific pair of mics. I've heard at least one person mention that their 'matched pair' of Oktava's didn't match too well when you looked at the relative levels of a recorded waveform. I'm not suggesting that any retailer is on the sly - just that you don't really know what response graphs you're getting if they're supplied.
Personally, I've been tempted to create a test disc of some frequency sweeps and do some recording off the home loudspeakers with each mic (in the same position, through the same channel of the preamp (to eliminate that as a possibility), same gain levels, same volume, same passage of music.. Just haven't got around to it.
I'm pretty sure you need a real anechoic chamber to do true frequency response, but for matching purposes I'd think you're OK as long as you use the same environment for both mics.
Anyone ever done this? (I know, it doesn't really help you with the original question).