The M5 is based on the 5 Series sedan, and it boasts a more powerful engine, upgraded wheels and tires, sport suspension, and aerodynamic styling. The most recent iteration of the M5 is the most powerful, but any pre-owned model is still a great choice for someone looking for luxury and performance. The M5s of the 80s and 90s were very strong performers in their time, but are hard to find today.
The most current generation of the M5 debuted in 2006, and of course it offered more performance and luxury than the 5 Series upon which it is based. The most notable change is its engine, where BMW wedged in a V10 putting out 500hp and 383 lb. ft. of torque. All that power gets to the wheels through a 7-speed sequential shift manual; drivers can also choose automatic mode or do the shifting themselves with paddle shifters. The main drawback was the M5's unrefined performance during in-town driving.
Plenty of R&D went into the drivetrain of the M5, but the suspension was focused on the basics. Unlike the 5 Series, the M5 did not have active steering, run flat tires and roll bars. However, it did have a finely-tuned suspension, electronic steering dampers, lightweight wheels, enormous brakes and high-performance tires. As was the case with previous M5 generations, the fourth-generation model didn't sacrifice much in the way of comfort.
Most BMW devotees regard the third-generation M5 as the best. The car on which it was based provided a great platform and was itself highly regarded for handling, styling and luxury. It was offered from 2000-2003, and included a 394hp V8. The only transmission option was a 6-speed manual; it came with 18" wheels and beefy brakes and suspension.