It's all up to what exactly you're looking for, the 1.9tdi will hurt the 320 every time, 0-100 and 100-140...
On the side, was looking for trouble the other night in my mates S5, and came across a heavily worked 1.9tdi (2 door), and although it didn't compare much to the S5, it sure as hell pulled so hard, riding on a cloud of soot!! It sounded awesome!