like m54 i have an e46 m sport model. there is a difference in the suspension of the 'sport' and 'executive' as the former sits about half an inch to an inch lower than the latter and has a staggered setup plus the M aerodynamic kit and emblems. i would think that this would also be the case for the new e90 model you are considering or maybe baka trim nga lang. sometimes the sales executive don't know any better than you do so just double check again with them.
you may also want to do a test drive of the two models so you'd get to experience firsthand any noticeable ride quality differences between them. at first i was wary of getting the m sport because on paper it was lower and had the sport suspension but after doing the test drive i found it to be comfortable and not at all jarring as i expected. you'd love how it takes the corners and both handling and steering feedback is more communicative since it seats lower and goes exactly where you point it.
'sublime driving experience' or as BMW would put it 'sheer driving pleasure.'
whichever you choose you won't go wrong. that's a nice problem to have
