Personally, I want to get the D3 simply because you can match it's illumination (color wise) to that of all the dash lighting. But some of my friends keep telling me to go with the new Kenwood Deck that has a 30 GB HDD. Thus eliminating the issue of only having GPS while the GPS disk is in the D3. That's the only downside I have with the D3. I don't know the model number for this Kenwood, nor have i seen it anywhere, but if you don't want to worry about swapping DVDs and the GPS disk, then I would say get the D3.
Out of the other two units, I would go with the Pioneer. I've seen both units and the pioneer has better image quality in my opinion. Sure Pioneer is known to have faulty RCA outputs, but I've only seen it happen when the SLA is tampered with.
P.S. - Sorry about going off topic for a while.