Right well if ur looking at specs of the two consoles, psp wins hands down
its a much faster console, has more memory and better graphics output.
But the nintendo DS while slower, has duel screen, 16 man wireless lan at 10mbps and touchscreen functions. Yeah ok so still looking at the two you would prefer the psp, i know i would if i had been given that information alone.
Now then, when you take a portable console out, your going to want to be able to play it ofcourse!
DS gives 6-10 hour playtime on a 4 hour charge (dependant on what game is being played)
PSP gives a kickass ............ 2.5 hours, which of these are really portable now? being required to change batterys that often is what first turned me away from the PSP, and into the light ... the Nintendo DS
ok so what you say, its the games that make a console what it is?
yes completely right
nintendo have stated it is possible to port any PSP game to the nintendo DS
While PSP could NEVER port ds games to them, the technology would have to be modifed too much to work.
DS already has one of the worlds leading game developers working on games for there console (Square-Enix) Creators of the Final Fantasy Series, which also by the way is being ported to DS.
Need for speed underground 2 and tony hawks underground 2 are availible on both consoles.
But these are the games im interested in at the moment, judge for your self which console brings more playability from.
im going to play it safe with the DS
Edit: A note on the media side for PSP
while it is true you can play mp3s and DVD's on it, you also need to buy the special format disks, retail around £30 each to play them. so basicly say you have ummmmm Blade 2 (on tv now

) on DVD and you would like to play it on your PSP, you would need to go buy Blade 2 psp version in the shops. That amount of money to play something on a 4 inch screen.
Another ploy by sony to get more money, remember the ps2? to get a fully working net enabled / hard-drive installed console was around $400 instead of the $200 the base iteself was sold for
go go sony, suck the money dry