The DS has innovative design (dual screens, touch screen, microphone ) and games that take advantage, along with many educational cartridges, and some backward compatibility to GBA. It comes in colours, yay! I have a GBA cartridge (Movie Player Advance) that would let we load media in with CF cards.
The PSP has a huge pretty screen and some compelling titles, including some new titles that may be language switchable (FF, FF II, according to IGN). It comes in black, like Ford intended. The PSP has UMD rom and MemoryStick rw capabilities. There is cool sync software for Mac OS X.
Nintendo is hacker-agnostic and generally targets all products toward youths, so there are almost no (1 so far?) 'mature' rated titles. Sony is evil, and uses lots of DRM and other nonsense to annoy hackers, who prevail anyway. Sony's hardware is substantially nicer. There are many many cool titles available for either platform in JP versions. Both have wifi and some wlan and internets capabilities like networked play. The price points are only 50 bucks apart.
So, that's what I know, but what do y'all say?