I have the TD4 engine and am very pleased with it. Plenty of power and torque. I test drove the SD4 and it didn't feel any different. I think that you would be happy with either so it is just the cost difference. I don't plan on tuning my engine.
I'm in the hunter valley. I have a td4 on order but I can get a sd4 from another dealer both coming about July. Just can't decide I have rang a few Sydney dealers and one says they mainly sell sd4 than others say they sell lots of td4 so really confused.