What exactly is better about the Mercedes or Audi? I had a Jaguar XJL before the Tesla and the only thing I see different is the massage seats and at that time...ventilated seats. I didn't realize there are more options that we are missing beyond that.
Tons of stuff. For example, Audi A8 and its ilk have electric rear seating reminiscent of an airplane seat in premium classes. I mean, more adjustable than Tesla's front seats in many ways. In the rear. With seat memory. And of course ventilation and massage (with many modes) available for rear as well... Some have electric fold-out ottomans... They have cooled places for your drinks (even integrated fridges). They have TV, they have AC inverters for your laptop, they have interior Wi-Fi etc.
They have ski passthroughs, they have rail systems in the wagons/SUVs (e.g. Q7) in the trunk, they have rear-seat controls for AC, media controls etc. as well as rear-screen systems. They have pull-out rear tables... vanity mirrors for rear, vanity mirrors with magnification options, all sorts of additional premium lighting. And of course the small things like lots of places for your coats, more drink holders etc. Plus the materials and attention to material detail is far superior to Tesla's.
To use Audi nomenclature, many of these things are also in the Audi A6, A7, Q7 range, which - even if one wouldn't place Model S/X in the A8 class - is at the very least very comparable to Model S/X. So certainly one is giving up a lot going Tesla in that regard. Recent steps like the Model X rear seating questions as well as this ventilation step are really going backwards for Tesla...
I like the Tesla dash. The small and the big screen and the front styling is actually perfectly OK in my view. Everything behind it, that is seriously lacking. (Assuming HUD is in the works for Tesla, because that of course is one thing in the front that is missing - that and 360 camera displays.)