So apples to apples:
Using 2014 curb weights (no options) -
M235i: 3535
228i: 3300
328i: 3400
428i: 3470
In my opinion, the 130 lbs over a 328i is worth the extra 100 hp / tq. But lets look at the bigger engine weights too
M235i: 3535
335i: 3555
435i: 3610
Still fatter than the M235i. Lose the moonroof and lose another 25-30 lbs.