[shivaswrath]

I've been driving an E90 for several days now (F30 in shop), and here's a more informed decision, and simple break down:
1. If you CARE about the interior of your car (looks, tech, feel), GET the F30. It's centuries more modern and welcoming of a driver's car than the E90 (the entire dash is virtually angled to the driver in the F30, harkening back to the E46 body style layout).
2. If you CARE about size and steering feel (small and tight), go with the E90/92 series with an N55 engine.

It's that simple...that, and you can take $ saved in dump it into aftermarket parts.