The difference is Tesla says you have to pay attention and enforces this, but it can attempt to drive on any street, make turns and lane changes, and navigate to your destination. Whereas Mercedes has a much, much simpler system that only works in a straight line going less than 40mph on certain freeways (so only in traffic).

Isn't this just for relatively low-speed driving, on freeways? IIRC it was limited to under 40 MPH, but on roads described in a way that it sounded like only freeways would qualify. I think there are lots of cars that can drive well under those conditions, though others won't assume the liability.

I think your analysis is right. I also would say Tesla FSD beta is clearly the winner of customer purchasable products. It's worth pointing out that Waymo and Cruise very often fall back to remote operators when the car gets confused. This is no problem if you're evaluating how successful they'll be at operating a taxi service, but makes it more difficult to compare to consumer systems that do not work that way.