I have both so think that qualifies me to answer. Guess which one stands the most? The 320d.
On long trips the 320d (4,2) the 330d (4,9). The gearing is longer on the 330d so is quiter and because of lower revs is very efficient.
The 320d sounds like a tractor where the 330d could almost pass as a petrol car with noisy injectors.
In town the 320d (5,2) the 330d (7.5).
At low speeds the 320d is adequate but higher up there is an enormous difference.:nonono: