I'm just wondering how many people have actually owned a motor of all of the above and can compare accordingly, or is it just first impression / on a whim here? Because I have, and a general breakdown in my experience is:
BMW 5 series - never had experience with a brand which required so much in the way of repairs and maintenance costs (except Range Rovers

). Features weren't all too impressive. There are some ludicrous design flaws with BMW too which makes it a magnet for thieves.
Merc ML and S class, A class - Very heavy handling for upper mid market cars. Features, again were nothing impressive.
Audi - A8 S-Line, Q7 S-Line - Basically get it right every time - Reliable, Speedy, Stylish, Hi-tech and Sleek. With the Q7, it's so light I just cannot believe it's technically a large SUV. Handles and feels almost like a hatchback. Cream of the crop for a pleasant ride here though is A8. It's so smooth that it feels almost like you're sitting in a plane. Every normal bump and dip becomes barely noticeable at ordinary speeds. The S Class didn't even come close in comparison to awesome user experience and comfort.
If we're speaking about models individually, the BM 8 series has always attracted my attention, if nothing but surprisingly eye catching aesthetic which has never been BM's strong point. Although people attempting to compare it to Aston Martins is just hilarious.
Merc A classes were ok, cheap and cheerful with a touch of elegance. Everything else though, Audi, hands down for me IMHO.