^^^OP, I own a '13 X3 35iMSport. I had the car serviced last week, and I was provided a '12 X3 28i as a loaner.

I was very impressed with the performance of the 28i. I did not expect the 28i to perform the way it did, but boy was I impressed. The 28i has considerably more torque than the old six cylinder 28i of yore. Don't let the four cylinder fool you...

I even provided my impressions of the 28i on the X3 Forums...

Long & short, the 28i revs a bit higher and stays in gear a bit longer than my 35i, but the performance was there...

Of interest, I found the 28i to be a bit un-economical. It might be b/c I did not drive it leisurely.

GL/Cheers,

BB