I used both the S6 and S2, and unfortunately, I handled the S2 after two shoots with the S6. Ultimately, while the IQ is the same (same sensor after all), the handling of the older camera was considerably worse, I didn't even know it lacked a joystick control! A friend looking to get into MF was with me and he was disappointed with the handling of the camera, and I couldn't blame him, there were just a lot of things we have taken for granted since the many years this camera has been out.
But what can I say? A lot of people find the Pentax 645D workable as a landscape camera, even though it is woefully slow for just about everything else. It depends on whether you see your camera as just a sensor in a box, or an ergonomic tool for active handling, there are a lot of good sensor-in-boxes that don't carry Leica branding on them, but the S006 is just so much nicer to use.