The '13 x3 has the auto start/stop (referred to as ASS by many ) and the turbo 4 which has slightly more power than the six.
Having driven both models I think the I6 is a better "drivers car" and it's exhaust note sounds fabulous. The turbo 4 is not as refined IMO
The only issue I had with the I6 equipped car I test drove was the throttle delay which made the accelerator pedal feel like a on/off switch. BMW has a TSB to address this issue.
Other than that I believe the earlier cars had some wind noise associated with the wing mirrors which was also resolved.
Personally? I like the new car smell. $10K is a fair bit of money... it's up to you.
Last edited by lbjgh; 03-07-2013 at 12:11 PM.