An extensive R&T review of two great sedans has the C55 winning by one point but the S4 kicking butt on the “subjective ratings”.
Something I can vouch for from the first night I drove mine:
“To the driver, wheeling the S4 is all the more satisfying, thanks to remarkably linear and reassuringly firm steering. It’s unflappable from corner entrance all the way through big power applications on corner exit, so the sensation is one of simply dialing in steering lock as required. This is uncanny when charging, as it feels the S4 will never run out of grip because the steering effort remains unchanged. Of course, the S4’s tires eventually approach their limits, as announced by a distinct notch of understeer magically appearing with Bela Lugosi flair at the stroke of cornering midnight. It’s as if the S4 gives free rein, then flips on the understeer switch just before any unpleasantness unfolds.”