id say e36 is actually less prone to rust! my mates an m3 nut, driven them ever since hes passed his test and he always swears his e36 was his perfect car (till a thieving git burnt it out)
personally i think there over rated, great track handling but in real life on the streets, if your giving it some and hit a pot hole then there real heart stoppers, i hate them, even refuse to drive any bmw in rain/snow
buy a diesel unless your going to actually use it on a track! thats my advice