I was smiling all the way up to Genting the other day with a 320d. Not sure how easy to do the same with a 320i. In addition, if you travel outstation often (eg Penang or JB) when you arrive at your destination, you will also be grinning when you look at the fuel gauge. Upgrade path for diesel is the power kit from BMW which will ensure your warranty is intact, but of course its the not cheapest solution compared to other 3rd party chip solutions. Test drive both for a longer distance, the only downside of 320D is that cabin noise is a bit higher when stationary.