Petrol v Diesel in Alfa engines

I do not wish to generate a large and unending discussion but would 
appreciate
confirmation of my own findings.

I have never owned a diesel car.

My 1999 Alfa 146 has 1.6 TS petrol engine and 89000 miles on the clock.
One of the really nice things with this car is that it will pull away 
from 20 mph
  in 5th gear so that once you are under way you can sail through 
roundabouts
and some junctions without changing gear.

Today I had a test drive of 1.9 Diesel GT Blackline special edition.
Engine was a bit noisy to start with but acceleration was fine.
However it would not pull away from 20 mph in 5th gear and I
found myself changing gear on a familiar route much more frequently
  than in my own Alfa.

I was always led to believe that diesel engines have masses of torque
at low revs but my experience proved to the contrary.
Do diesel cars need to be driven in a different way of which I am unaware
?

John Chapman