You must go there for full size samples:
D800=M9 resolution-- raw pictures: Nikon D3 - D1 / D700 Forum: Digital Photography Review
Leica M9 is 18 Mpix, D800 36 Mpix.
I pulled relevant raws from Imaging Resource comparometer (Still Life at base ISO, dng and nef).
I developed them in Raw Therapee at default, no post. I saved them at full jpegs: 11MB for Leica and 20MB for Nikon. The jpegs do not differ visually from raws, if somebody offers bandwidth I can deliver tiffs (100MB in case of D800).
I do not see any differences in real detail between the two cameras. But please help to find any. In fact I prefer the Leica picture. When printed in A2 on my Epson 3880 the preference for Leica is even stronger.
See the attached jpegs which you can pull from my gallery in their full glory of 11MB and 20MB respectively (full original download enabled).