Yes, they're were huge changes made starting in about 2003 withthe advent of higher pressures, comon rails more electronic control over injector function. All of these changes were for power, reliability and efficiency (emissions). And that's just with engines. Transmission made leaps in efficiency and operation as well with the new electronic systems that control them.
Personally, I would opt for one of the newer powertrains over the previous generations. They run nicer, smoother, more quiet make more power and get the same or better fuel mileage as the the older models. They're also more reliable - but harder to work on for the DIY'r.
