Mark, after processing I don’t see much of a difference in the files at full resolution. I sent the original two images to our mutual friend Andre and he picked the Leica image correctly. When I asked him what he was looking at he pointed to the portion of the image which I’ve attached below. Keep in mind he only had web sized images to work with. It’s quite possible he sees something that I don’t…but to me they are close enough to be indistinguishable from an IQ perspective. I’ll keep you posted as I use this lens more.
I’m not sure I’m the best person to answer your question on whether the adapter and a long lens would be a good choice. I’ve shot with all the super telephotos from both Nikon and Canon and think they are superb. And the AF on both those systems is light years better than a Contax lens on the S2 would be. Add in the limiting ISO on the S2 system…well, you get my point. Over the years I’ve seen several photographers try to move to MF for wildlife and none of them succeeded. But with a sturdy tripod, good technique and a non-moving subject…you might pull it off.