DS Lite was good. Some decent solid games there. Backwars compat. with GBA along with some nice add-on features only available by using both slots on the machine. Plus touch screen adds a new depth to gameplay.
Gameplay which, at best, is consistently shallow anyway.
Like I said, some decent solid games... But not many. It kinda makes me wonder what some people mean when they say 'DS is a purely gaming machine'. Bullshit. Brain Training. I rest my case.
And those who say 'DSi owns PSP', have you forgotten something? The DSi's camera is something like 0.3 megapixels. My 2 year old phone has a better camera than that. And it can play music now!!! So what? MP3 player much? They cost about Ł15 for a 2 gig one. Saves on you buying a Ł20 SD card. Oh, and as Ishi mentioned, the lack of backwards compatibility = lack of second-slot functions = lack of gameplay = even wrose. Updating to a DSi is really a well disguised and expensive downgrade.
That said, PSP has emulators, always had built-in media functions, has a good variety of good games (and not gimmicky shit like Cooking Mama), decent online capabilities (lets face it, Nintendo suck for online functionality), a new, yet somewhat familiar, control setup, and its not hard to port homebrew. That, and CAVE STORY (which is reason enough why PSP is better).
The DS only has two real saving graces; Phoenix Wright and Elite Beat Agents.