Both very reliable, the beemers are great. Thing is, you will get 10 years hassle free driving from the ZRE, but the E46 is right at its time of faults starting to happen, things wearing out etc etc.. As a beemer owner and lover, the amount of cash ive dumped on my beemer over the last 4-5 years could have almost paid for 1/2 of the car. tough call, they are really very hard to compare two totally different cars.