I've not had a diesel so can't comment but i've had all the old petrol engines and indeed all were good at something!

My first was the 2.016V, with a manual box it was a screamer! Big smiles and great for round town as well. Can't remember fuel figures or anything but think it was similar to the v6s i've had since! It did have to work hard I suppose, although as the car was a Select (read sooo basic - even wind up windows in the back!), this probably made it lighter too!
When i moved onto a 3 litre v6, with an automatic as well, the noise was the first impression

8-)

. and the effortless motorway driving. it thought nothing of overtaking - even with a caravan apparently!
Now I'm onto the 2.5v6 with a manual and find it often to be as quick as the 3.0, slightly more economical (just) and quite capable with loads too. My only gripe is on the motorway, 5th gear seems pointless. shame it wasn't geared to drop more than 400 revs!
I wonder about giving it more power, not sure if that's because i find it slower or just know that it is less powerful than the 3litre! :-/
There's also something about having a burbly v6 rather than a 16v lump that astra's get too.... 8-)