Pen
I have both adaptors.
Got the DSA-N1 first. It is light/compact and easier (relative to the DSB-N1) to balance on the scope with the camera. As it is fully manual, you got to be dexterious enough to get subject in frame, focus scope and press the electronic shutter release quickly. This setup, however, is great for those very obliging subjects that remain still on a perch for minutes. The sad part about the electronic shutter release is that you could only shoot one shot at a time and it take 1-2 seconds for the camera to write image to card before you could shoot again.
As for the DSB-N1, it is was bulkier and take longer time to attach to the camera and scope. You can shoot at autofocus mode but it is still the focus on the scope that really matter. Even though the camera focus box turn green when you depressed the shutter half-way, it does not guarantee that a good focus is obtained. Also when at autofocus mode, you cannot zoom in onto the subject to get a bigger image which is available in manual mode. The big plus point the DSB-N1 has over the DSA-N1 is the manual cable release which would allow you to shoot in continous mode.
With regards to the IQ differences, you may refer to my flickr photostreams (
http://www.flickr.com/photos/53435640@N05/). To me, the IQ of images shot with both adaptors looked pretty much the same to me.
Hope my two cents worth of feedback helps.