BMW is surely the winner on the technical specs. But I think the newer Audi's look much nicer specially with those leds headlights. But BMW is still the better choice indeed.
Mercedes is just a brand. if you know the history of Mercedes you know why.. Mercedes used to custom make their cars fully in Germany but they had big problems making the cars profitable as making them was almost same expensive as selling them. So later a few years back they decided to hand out all their parts making to cheap chineese factory's and since then Mercedes have never been what they really where. Its just the brand making you feel like you got something good, but in fact your driving and 70% cheap chinese factory made vehicle
and you really notice this on the quality.