some interesting points made here, and I take issue with the concept of audi=crap, and also with some of the BM/Merc points.. My last three motors:
B6 A4 tdi sport (Mods: AMD remap only) covered 59K miles from new
BMW 330d sport (Mods: Black diamond discs and pads, Eibach springs, other minor stuff) bought at 40K and covered another 28K miles
CLK 430 avantgarde (Mods: Eibach springs, Eisenmann race exhaust) bought at 88k and covered another 45K miles so far
Out of the box, the best all-round drive was the A4. Both the BMW and the Merc had too soft suspension, despite being alleged 'sport' versions. The Merc was the worst 'as standard' but was the most transformed by the modifications.
Best drive after mods: CLK, no question - but not really fair to compare a huge torque and fairly free revving 4.3 V8 petrol and nearly 300Bhp with the other two engines, and once the handling was sorted thats what made the difference. It was the most 'crippled' by standard suspension though..
Best on Fuel: A4, by a country mile. didnt really matter how you drove, dont think I ever got less than 500 miles out of a tank and it was usually around 570. Savings here were way offset by other costs though.. The BMW 3.0 diesel (auto) rarely topped 32mpg (got 37 on a good run once) unless you were 'driving miss daisy' - and why buy that sort of car to drive like that? CLK consistent 24mpg, which given unleaded is cheaper I view as acceptable.
Other running costs: A4 the worst by a huge margin, even putting aside depreciation (the other two werent new, so unfair to compare that). Audi servicing and parts costs were frankly appalling, neither was it that reliable - 5 or 6 PITA issues in 60K (under warranty true, but still involved courtesy or hire cars and frustration) and included replacement gearbox and oil pump etc. BMW had minor issues, bushes etc and odd electrical gremlins but basically not too bad, and big savings on servicing.. (and gearbox not needing oil changes every 40k etc!). Merc: fantastic, £270 for main dealer big service.. come on Audi thats how it should be! have just switched to independent and its better still.. Merc is also the best on tyres, which I didnt expect..
gearbox (all auto): A4 worst, dreadful, reported regular errors, fresh oil at 40k compulsory, needed replacement at just 35K. (ok, was a PITA so I'm biased against it!). Merc 5spd Auto hugely the best, locks torque converter in top 3 gears (so you still have engine braking), sensible ranges, fast changes, tip works well, superb. BMW - no problems, but slowish changes and unremarkable (even BMW forums call them a 'slushbox' and its a good name).
Reliability:
the Merc, best by a mile! (Also didnt expect that!) in 45K miles Ive had a single fault: a Xenon bulb which started to fail, went purple and cost £29 to replace.. other than that just routine servicing, no gremlins, no faults, no creaks, no rattles, just superb.
Would I buy them again?
A4: Yes, no question - but would not buy new. I would buy at three years old, get one which has folding rear seats, and use independent for servicing. Would be very very tempted by a B6 S4 V8.
BMW: No, probably not. It was neither one thing nor t'other, was respectably quick and comfortable, but never quite hit the mark. M3 might be awesome, but just not quite.. well.. you know.
CLK: Have to say yes, if only because after 45K I don't have the slightest urge to replace it, but I would definately NOT buy it new, and the modifications were absolutely essential to the drive, more so than on the other two.
Interior/seats: A4 wins, then Merc, then Beemer.
think i strayed a bit off topic :-(
NONE of them were crap!
