I went from a GTi 6 to a 335i (F30) its such an awesome motor, in my opinion you not doing heavy mileage to worry too much about fuel consumption! I know its a concern but not top of my list when buying a car.
I've never driven the 2.0d's but then I knew what I wanted and it was the 335i in my case.
I was also shopping around for a low mileage 335 but they had only been out for just less than a year and I was offered one at the same price I could get a 2nd hand one with 20k on the clock, granted it wasnt as specced up. I wasnever really interested in all theose addition gadgets in the 1st place.
So I would say drive both and see what you prefer.
Hey you can always get the 120d now and next year upgrade to the M135i
The mileage of 15000 km a year may be a bit low to warrant a diesel, especially since you only keep the car for a year or two (but this all depends on the purchase price and spec, as you may get a pre-owned one at a good price).
I have a F20 120d+PPK and have so far covered 54000 km in 23 months, but then again, break even cost calculations do not take into account the diesel torque fun factor in everyday driving conditions.
Another option in your price range is a pre-owned F30 335i, you save on the initial depreciation and can still add a PPK.
There is a 2013 M135i manual at Vereeniging dealership 6000km on clock for R429000. This car has probably lost as much value as it is going to.Seeing you only keep a car a short while might be something to look into.
White one?
I had fun in this little monster, led me to buying mine. If it's the one I took on a drive it only has the leather seats and nothing else as option