I wasn't quite clear on what the OP is trying to say -- but I just don't understand how someone can drive the 135i and claim it has the same interior space as a 3.
My friend has a 135i and the car feels tiny. With four people in it its downright claustrophobic. And seems like half the cargo space.
Car sizes go in cycles; expanding and contracting based on the times. People are claiming a new "renaissance" of interest in smaller, more compact, and lighter weight vehicles, but really it just the cycle continuing.