mowe on 17 October 2008
Well, I think that the DS has a lot more variety in their games, but how good the library is depends solely on what kind of games you like. If you invest in a 20-30 dollar flash cart, then you will be able to use your DS for some media capabilities like playing music, watching videos, etc. Not to mention illegal ROM's for free, but you can do that kinda stuff with the PSP, too.
Buying a PSP now and selling it later for the DSi would also be a good option, but you will probably hang on to your PSP once you get it (unless you want both).
# of games above 75 on Metacritic (including downloadable):
360: 241 DS: 144
PS3: 152 PSP: 126
Wii: 85
