If you look at the difference in interior measurements, there is so little difference between the two that its pretty insignificant. The significantly smaller look of the exterior makes most think there is a huge difference. The backseat headroom of the 1 is actually better than the 3 due to the different shape of the roof.
It was funny to look at the 92 Mustang 5.0 coupe parked next to me when I picked my kids up from school the other day. My 135 looked bigger than it! I used to own a 93 coupe and that thing felt Iike a much larger car than my BMW does.
Finally delivered!!...2012 135i/AW over Coral Red/MSport/Nav/HK/Toasty Seats/6MT