I currently own an e92 M3 and have owned an e39 M5; both cars and their respective engines are automotive masterpieces.
IMO there is no let down in neither one, it is not just the engine, it is about complete package.
Bulletproof engine, instant torque feel, smooth highway cruiser = S62 . e39
High rpm strung engine, more flexible, pure driving excitement at all times = S65 . e92 / FEI - there is plenty of torque available in the
S65 engine, just have to drive the car like it is meant to be driven...
If you really like driving you would enjoy both with its own characteristics.
12 FROZEN SILVER E92 M3
03 GP WHITE S2K AP1
13 MONTECARLO BLUE F10 M5
PREVIOUS M CARS
02 LEMANS BLUE E39 M5
06 SAPPHIRE BLACK E60 M5