The UrS Audis are great cars as well, I almost bought an S4 locally last year. They can be easily modified for absolutely silly power, that's probably one advantage over the M5.

I've owned both - sort of. I owned a e28 535is and a ur-M6 as well as a ur-S4 and 95.5 S6.

Are you serious?

Yes. I'm investigating both for a potential future purchase.

Owned a 1988 M5 that was a low numbered car when the lawsuit was settled. Received the settlement from BMW right after I sold the car. My recollection is that the voucher was purchased back by BMW for .75 cent on the dollar. Sold the car for more then I paid and then received the settlement back from BMW which made this a sweet deal comming and going. Just pure luck that I owned it during the lawsuit and was able to sell it for more then I paid for it. All in all, a great deal on the front end and the back end.
Without question one of the fastest cars that I have ever driven. A great car that to this day I regret getting rid of. Unfortunately, my wife was scared to drive it and wanted something more "reasonable" to haul the kids around. I do remember the cost of service @ the dealership being crazy because it needed to be serviced by a "M-5" mechanic and parts costing 25% more then the standard run of the mill BMW. The invoices where shockingly expensive:eek::eek:.....to say it was expensive to have the car fixed/serviced at the dealership would be a huge understatement.
I relented and sold it for the Honda that she wanted. Talk about love clouding your decisions!
The most fun 4 door sedan that I ever owned/driven and highly recommend ;)...

The comparison has to boil down to use.

The Audi would make a better daily driver, and a better all-weather car. It is a quiet, comfortable, luxurious grand tourer when you are commuting, and your personal rocketship when you hoon it. Perfect rooster-tail-shooting four-wheel-drifts are possible if you want to play rally car driver for the day.

The BMW is more engaging, visceral, and 'light'. It's a sports car with sedan sheetmetal. It's not as luxurious. It's not as quiet. It's not as comfortable. The clutch is heavier in stop-n-go driving. But it is the ultimate partner in crime on any twisty back road or deserted freeway.

The Audi's engine is robust and just a boost-tweek away from big power. But it does it without fanfare. The M's engine is, again, engaging and intoxicating. And expensive. But both engines are pretty bulletproof. Both gearboxes can have troubles. Both are expensive to fix, overall, anything M-related will make you gasp.

The M5 would be more 'fun' but isn't that what a 911 is for? Buy the ur- S4/S6 as a DD and have a 911 for a toy.

E

I revived this thread because of this very recent video at Petrolicious.

BMW M5 Is Power & Speed in an Unassuming Frame | Articles