The RS4 was the most recent drive, a too-quick trip from San Francisco to Monterey and back. And while ultimately, I think the C63 is the best of the trio, there's plenty of reason to think about (daydream about, drool over) the RS4, even though its $66,900 pricetag is more than $10,000 dearer than that stuck to the Benz or the Bimmer. (On top of that, you'll pay a $2100 gas-guzzler tax for its 13/20 mpg fuel economy, and $775 in destination charges.)
The Audi's pleasures are a little subtler than either of its country cousins. Even in dark metallic grey, the C63 I drove wore its body add-ons like a popped collar. On the RS4, the aero kit's much more discreet -- a shallower wheel flare, a thinner side skirt, and a virtual banishment of chrome. Against the stop-sign red M3 I last drove, the Audi was only a shadow. Even the wheels were painted pewter on my car, thanks to a $750 Titanium package, a quietly stunning detail. Inside, the finishes are subdued, too, all rich Alcantara and leather and piano-black trim.
The big differentiation in the drivetrains is Audi's hallmark quattro all-wheel drive. It imparts a much different feel than the tail-happy Benz and BMW. They're never out of control but they can be provoked; the Audi's positively judicial in the way it doles out power with authority, never misplacing a pound-foot. That power - 420 horsepower and 317 pound-feet of torque - issues from the 4.2-liter V-8 in a steady flow through a six-speed manual gearbox that's a pleasure to shift, which ain't always the case with Audis. Steering and braking are in total concert in effort and responsiveness. And even with big 19-inch wheels, the muted thumps of the 101 heading out of Salinas are dispatched with an even hand, though you'll hear every one.
One last note: the iPod connector tucked into the Audi's glove box is a decent half-step, but the automotive world is about 18 months behind in adapting to the iPhone. Audi's in that crowd: when you plug the iPhone into the snug-fitting adaptor, the phone antenna promptly shuts off its wireless signal since it's "not an approved accessory." So you'll have to choose between Amy Winehouse and your boss.
Before you make a pick, think about it. Who's going to be more entertaining while you cruise at a swift 85 mph in stealth mode? I thought so.