I happen to have both the WATE and the Voigtländer Super Wide Heliar Aspherical 15 mm 3,5 - and the M8 - and the M9 right now. Due to the manual lens compensation set on M9 the Voigtländer becomes 'quite a lens' on the M9. I have the non rangefinder coupled version and found it far inferior to the WATE on my M8. Nor had I any IR/UV filter for it, while I had the full filter set for the WATE. - Even without the filters the WATE was far better, Particularly corner sharpness. The WATE draws nicer, finds more details in the shaddows and reproduces glass and silverwear almost 3-dimensional, while the tiny Voigländer puts a fog on everything.
But this the increased resolution and the possibility of manually set the lens compensation, the Voigtländer Super Wide becomes far better on the M9....