Is performance the first thing you consider when buying a diesel? I
wouldn't say so. 9 times out of 10 people going for a diesel want
economy first, obviously.

What I meant before is that no matter what I said when I was looking
at the 159 the salesman always tried to push the diesel. I went over
to the brera for a look and salesmen said "that's available in a
diesel as well!". I ended up not buying either.

My advice, test drive both petrol and diesel work out the difference
in purchase price and cost of fuel. Think the diesel is about 2K more
than the petrol to buy new and certainly round my area diesel is 5-10p
per litre dearer than petrol.