Digital BW, The Print

In a user's review of the Leica MM at http://blog.mingthein.com/2012/05/23/leica-m-monochrom/ the reviewer has a screen shot of a series of 100% crops that compare the RGB sensor with the B&W one at different ISO's.  It's the most objective comparison I've seen yet.  See 
http://farm9.staticflickr.com/8146/7248163262_853753c3bb_o.jpg

I suspect the comparison would be about the same for any type of sensor.

(Thanks to the Leica Users Group for notice of this review.)

Paul
www.PaulRoark.com