The resolution difference isn't a factor of 2 in both dimensions, comparisons of the M Monochrom and the corresponding color model rather hint to the factor of

The resolution difference isn't a factor of 2 in both dimensions, comparisons of the M Monochrom and the corresponding color model rather hint to the factor of 2 in the total pixel count which is expected from the mechanics of the color interpolation process. But still it is a noticeable resolution gain. And indeed, you also get at least a stop of exposure.