I had a 2.4jtdm 159 and absolutely loved the engine. It was the best diesel engine I'd ever had - exceeding even the excellent 2.7 twin turbo Jag engine. I haven't had the 1.9 in an Alfa, but had basically the same engine in a Vectra and thought that was an excellent engine as well - plenty of midrange torque and quite unbelievably good economy (around 50mpg). By contrast, I only managed around 35/36 out of the 2.4.
It all comes down to your priorities in the end; the 2.4 is undeniably a lot quicker, but the 1.9 is plenty fast enough to be fun. If you don't mind paying for the extra fuel and wear and tear of the 2.4, then go for it; but if you opt for the 1.9, I don't think you'll be disappointed. Do take note of the comment above re the DPF if you do short runs - my 2.4 needed about 6 miles to reach the temperature that triggered the DPF Regen, and you then need at least another 5 minutes of driving for the Regen. to complete. If your journey's aren't suitable for this to happen, you're in for expensive blockages......
Last edited by 159john; 22-10-13 at 09:26.