I don't believe you would be unhappy with either the 2.7 or the 3.0, both are great engines that power a 2.5 ton vehicle very well. You need to decide what kind of use your D4 will mainly be used for then decide which one suits your needs best.
Personally I'm happy with our 2.7 even though we tow a 2.5 ton van often, yes the 3 litre is very nice to drive and has heaps of power to burn but power isn't always everything when deciding what vehicle to buy.
cheers,
Terry

