At our dealership, E46's are are very reliable as long as their maintenance has been done. We find that E90's also have been reliable. We sell 6 to 10 E90's per week with little or no issues. Then again we do pay more to purchase straight from BMW credit. Mostly we do bushings, control arms, abs lights and sensors. Which ever you buy have it inspected independently, purchase a comprehensive warranty and maintain it properly. You should minimal issues.
Good luck.