PD170 was again a good engine but suffered DPF problems but this wasn't really VW's fault, was forced upon them.
Common rail engines are MUCH better than the PD engines.. I had a pd for nearly 3 years and tuned it and now also have a CR170 and have tuned that.. CR smoother, quieter, more refined, better response, only "downside" is harder to tune (much more complex to map) and more expensive because they're new.