AT this point, I fool around with my PSP more; but even though I got it at launch, it still has that"newness" feeling to it.
However, I pretty much burned out all the games I wanted to play on it (which were Need for Speed, Ridge Racer, Untold Legends, Twisted Metal and Lumines).
I recently bought a 1 gig pro duo card, and have had fun ripping movies and magazines to it.
However, looking down the road, I see the DS getting more play. Between Castlevania, Animal Crossing, and Advance Wars there are some pretty sweet games coming for it that I actually want to play.
The PSP? Not so much. Midnight Club 3 looks hot, but do I really need another racing game? No. (at least not until Burnout arrives...)
I have no interest in GTA, Coded arms, or any other of the upcoming games, except for maybe Virtua Tennis, Infected, and the aforementioned Burnout.
So I'd say (and two months ago, i never thought I'd ever being saying it) go with a DS.