You probably made a small typo, for an MC noise voltage plays a dominant role and noise current is insignificant because of the very low Cart resistance.
That's why you can use op-amp's with only 0.9nV/rtHz like the AD797, but with a noise current of 2pA/rtHz that would be detrimental for an MM.
Fet Op-Amps don't go much lower as 4nV/rtHz, so the choice is easy in favour of the Bipolar.
