DS PRO'S:
-Touchscreen.
-Biggest 3th party support.
-Nintendo games.
-Big software line-up.
-Interactive... Fun to play FPS like metroid... Or minigames like Warioware... And brain training or even Sudoku is much more fun than on PSP.
DS CON'S:
-Not a graphical beast (N64 lvl's).
-If u don't like a touchscreen... (Which i can't imagine cause it feels rather normal or should i say... natural?!)
PSP PRO'S:
-Nice graphics... (PS2-)
-God Of War: Chains of olympus...
-Big screen...
-Many options... (Plays MP3, MPEG4 etc...)
-More FPS orientated games...
PSP CON'S:
-Battery dies in 3-10 hours... Depending on if your watching a movie or playing a game like Sudoku...
-Less games...
-No touchscreen (If u don't like a touchscreen forget about this con)
-Sony games... (Not as good as Nintendo's in my opinion but still GOOD)... Example: SoCoM Fireteam Bravo 2...
Edit:
I have 1 DS and 2 DSlite!...
Cause i like the games and the touchscreen... And like to play multiplayer metroid and stuff... But thats just me...
I'd pick DS... (But im a Nintendo fanboy...) So it's your choice... But i'd say DS! (And 40 mil to roughly 20 mil agree with me...)
THE NETHERLANDS