Which car is better and what are the benefits of the 840 and the 850. Also which years are the best years for the 840 and the 850.

first off both of the cars are old. they discontinued the 8 series in 1998 or 99 so no matter what you would be getting an older one. if you do get one get a 98 or 99 since it would be the newest one. which is still old. the only difference between an 840 and an 850 is engines. 840 has a v8 and the 850 has a v12. i would only get one of these cars if you are a fan of bmw and have money to throw around. don't get it for your primary transportation vehicle as older cars ESPECIALLY bmw are unreliable as they age. so yeah...

Definitely 850 is much better.