My husband just got the Z2 and I just got the D3. We both like our own best.
I would like the bigger screen. And I didn't play with the voice recognition much on his. But other than that, I'm happy with the D3.
I play my ipod 99% of the time, so it's no big deal to me to have the nav disc in all the time. I don't need another (small) hard drive of music to try to manage (besides my iphone, ipod, laptop, big home external, small travel external).