I own both the 5DII and the M9. I don't own the Nocti, but I have used it plenty of times.
One thing I can tell you is that at low ISO (400 and under), the CCD of the M9 destroys the 5DII (and even my 1DX) - You heard it.
Yes, everyone likes to dog on Leica shooters, but it's a great tool that when coupled with Leica glass is an absolute beast.
FYI the Nocti actually costs closer to 11K new