BAV man
328 Ci.......
Coupes are slightly wider and longer than the sedans. They are also set lower and stiffer, so there are some differences in the suspension components. (not sure which parts differ)
The windows... Beware of metallic springy sounds emitted whilst opening or closing as this denotes pending failure of window lifters, which cost a bomb on the coupe.As BMWCAR pointed out, make sure they come down when you pull on the door release and that they go back up fully when the door is closed.
A word of warning when applying tinting to the windows. The thickness of the tint seems detrimental to the rubber seal ( on my car anyway....) It makes the rubber act like a squeege when the glass is wet, and produces a screeching sound when operated. It could just be that my felt bits are a bit hard. Not to sure about that. Or the increased thickness is pressing it too tightly... who knows?
The coupes do not share any common body panels with the sedan, so that might be an issue when looking for spares. Even the headlamps, tailights and even the boot lid is different. For example, a boot spoiler for the sedan will not fit a coupe properly.
Things like the interior trim bits ( ie brushed, CF or cube) is not the same as it attaches to the door armrest and not the door panel.
The long and short of it all is... IMHO all 3 series look better in 2 door form. It's just that most people want the practicality of the sedan. It's your call at the end of the day.
Also,IF I have my figures right.... the 328's torque (280nm) is very close to the 330's ( 300nm) even though the bhp of the 325 is almost identical to the 328.... the 325's torque (245nm) is significantly lower...
Here are a few reviews to fuel your imagination
http://www.bmwworld.com/reviews/328ci.htm
http://www.racq.com.au/cps/rde/xchg/SID-34...ci_ENA_HTML.htm
Enjoy your search!