well the main diff between a 318 and a 330 is engine size. the 318 is a 4 cylinder 115hp? i forget the number. the 330 is a 6 cylinder 225hp. Besides the engine, there are small visual and luxury elements. Usually its no comparison between these two cars. BTW, the 318 only is in the E36 (older body style) whereas the 330 is the E46 new body style. (this is in the USA only)
a manual 330 is pretty quick. some have reached 5.7-5.9 0-60mph which is very respectable. no doubt beating any honda (maybe not the s2000) any toyota...you get the picture.
but in honesty, what a car can beat in a race shouldnt even be a factor when buying a car.
Two completely different classes of vehicles bro. Not dogging you in anyway but you can't seriously be considering an S-Runner and a 3/5 series BMW at the same time.
If you need something to haul/carry stuff, get a truck. If you want to straight line, get a Stang or something. If you want refinement and performance, get the BMW.
Good luck with your search....