[Cyberdemon]

My suggestion:

Test drive a 228i that is as close to optioned as how you would like it. IE if you want a sport/M sport car, do not try to judge a base no line car. The handling characteristics are very noticeable.

Once you drive it, decide if it has enough power, noise and grunt for you. If it does, stop, drive back to the dealer and order it.

If you're left wanting more, then drive the 235.

Do NOT try to reverse the order. Once you drive the 6 it's highly unlikely you'll want to drop back down to the 4 cylinder. I test drove a 328 after shopping for 335i's and it didn't have enough emotion to make me not splurge for the 335.

Ultimately the delta between a similar spec of 228i and 235i is around $4k. If you chose a stripped down build then you will save more money on the 228. So if you like checking the option boxes, the jump to a 235 may not be a big deal.

In the real world though, a 228 will have enough performance and speed to get you into plenty of trouble, even on the track. But if you're like most gear heads who like the extra slew of M badges and mechanical noises that come out of the 6 then the answer will become obvious after a test drive.