Audi RS4 Avant versus Mercedes-AMG C-Class C63 S (W205). 0 points of retained value between them.
At new money, the C63 S was actually cheaper per horsepower than the RS4 Avant — £132 versus £139 per bhp — and that gap only widens on the used market as the AMG has depreciated harder. You're getting 503 bhp from a 4.0-litre twin-turbo V8, 291 bhp per tonne, and a car that does 0-62 in 3.9 seconds with a soundtrack that no turbocharged six-cylinder Audi can touch. The RS4 is measurably slower, measurably less powerful, and measurably heavier relative to its outputs. On paper, the Mercedes wins comfortably. The character gap is where it becomes a no-contest. The W205 C63 S is widely regarded as the last genuinely unhinged AMG saloon before the brand started smoothing its rougher edges, and that cultural moment has real monetary value now. Rear-wheel drive, a V8 that makes the right noises at the wrong times, and handling that rewards commitment rather than just managing risk — this is a car you remember. The RS4 Avant is accomplished, practical, and quietly fast in a way that impresses but doesn't stay with you. The RS4 makes sense if an estate body and Quattro all-weather traction are genuine requirements, not optional extras. But if you're treating this as a performance purchase first, the C63 S offers more horsepower, more theatre, and more future rarity for less money per bhp. Buy the AMG before the market works out it should cost more.