I got a DS over a PSP because of the price, the problems, and the games.
The DS was easily $100 cheaper
It didn't have stuck pixels or a square button that doesn't work right because it's too close to the screen
And it's got all the weird, wacky, and experimental games like Wario Ware: Touched, Meteos, and Phoenix Wright: Ace Attorney along with the great games like Castlevania: Dawn of Sorrow, Metroid Prime: Hunters, and Super Mario Bros.
I loves my DS, and I loves it to the point that I will trade it in to get the newest iteration (since the new one is better).
As for RPGs, well there's a new one coming out for the DS called 'Contact' I believe that has a similar art style to Earthbound. It's going to be an MMORPG that uses the DS's Wi-Fi. (More Info
here.) It's also going to have the remake of the heretofore unreleased (in the US) Final Fantasy III with updated 3D graphics. This isn't the FF3 we had, that was FF6. This is original game from the NES updated to a new glory. (more info
here.)
Initiate discovery! Fire the Machines! Throw the switch Igor! THROW THE F***ING SWITCH!