You piqued my interest. I played loud white noise on my stereo and recorded with the internal mics and some Church mics. I can definitely see less lower frequency content in the internals. And, of course, my speakers and other components play a role, although they generally seem to be pretty flat.
[Edited as suggested below by Brian Skalinder to reflect linear scale on both. My bad. Also reduced image sizes a bit more. Although I do not understand guysonics following note, I did record the internals on the "hi" mic sensitivity since the levels were so low with the "low" setting.]
With the M10 internal mics:
With Church mics > M10: