I know it sounds silly, ofcourse the N4 would be better, its a later model!
But according to the Pioneer website, the N4 has a smaller screen (6.5" to the N3's 7") and lacks some serious functionality.
On the Pioneer site, it says that the N4 retails for $1,600, and the N3 for $1,800 - which makes me think I am getting more stuff in the N3...
On the product comparison page, you can check out some serious diffrences:
N4 has customizable background images, the N3 does not
but then it says you can upload pictures to the N3, but not the N4
N4 has 12 million POI, the N3 only 11 mi