OK... lets look at the pros and cons of each console...
PSP,
Pro, Can play movies
Con, Movies are only available from Sony on specially designed memory sticks.
con, movies are write protected and cannot be coppied.
con, the screen isn't really all that great for viewing movies and lacks true colur depth
con, the battery life isn't actually good enough to watch a whole movie without having it plugged in.
Pro, made by Sony -Gets lots of exclusive titles?
pro, wireless gameplay
con, expensive
DS,
Pro, Movie support planned, to fit on flash cartridges that are freely available to buy.
pro, Music support planned, again on the freely available flash cartiriges
pro, Touch screen for interaction.
pro, microsoft for sound interaction in games.
pro, two screens, (often one can contain a map or inventory)
pro, backwards compatible with GBA games.
pro, cheaper than the PSP
Con, a little on the large side.