So, is the Sony A7r a Leica killer? Or does the Leica M still have some advantages over the Sony?
Obviously we are comparing apple and oranges. Shooting with a rangefinder camera is quite a different thing! That said on the pure Image Quality front we can report a small surprise. While the A7r beats the Leica M in many aspects (overall resolution, dynamic range, color rendition) the Leica M still shows a clear advantage over the A7r: The corner performance of the Leica is considerably better!
In the center, the A7R has much higher resolution than the Leica 240; it’s 36 megapixels versus 24, after all. But the corner numbers are more interesting. Here the Leica camera has resolution slightly higher than the A7R.
And if you want to “see” the difference watch this test made by Stilgar:
Center crop and corner crop too: http://www.flickr.com/photos/stilgarnaib/sets/72157638447272734/
This means that the Leica M still shows a much better performance particularly with wide angle lenses. Something you have to take into consideration if you shoot mostly with that kind of lenses!