To tell the truth I like the DS series better because they got more and better games than the PSP. So basicially the PSP is a traveling MP3 and it losing to the DS anyway so I say DS hit the most moneys the whole way through.
Anyway, I'll have to go with the PSP. It's far more durable, has had a DLC store for a while now, and can easily hook up with your PC with a mini-USB cable.