The 20d is very noisy (from the outside - it's quiet inside). If I was buying now I would spend the extra and get a 30d. The fuel economy is almost the same and you can drive it conservatively but have a little extra when required -auto also standard but you factor that into the price difference assuming you want an auto.
This is coming from someone who has driven the 20d for almost 2 years now. Still love the car but given the choice (I had no choice as no 30d when I ordered) I would recommend the 30d over the 20d
BMW X3 (F25) xDrive20d SE . . titanium silver . . titanium front grille . . 309s . . xline . . xenons . . black leather . . alu trim . . professional multimedia package . . dynamic package . . climate package . . electric seats . . folding mirrors . . servotronic steering . . DAB radio . . business speakers . . sun protection glass . . split rear seats . .