ok guys, well i have a psp, my cousin has a ds and i have had quite alot of experience with both. Ok firstly my opinion, PSP is better but DS have some kool features that psp doesn't but overall psp is better. As far as the battery life is concerned depends on what you are doing, with mine from one single charge i get 9 hjours of continuous music playing (yes i have tested all these) 6-7 hours constant video watching on umd which is the same for playing a game. Watching off mem stick is roughlty 7 n a half. Ds is good i find with that around 6-7 na half hours constant. I like the touch screen on the ds buti find it really does lack in the graphics department compared to psp. The screen on the psp is ownage to any hand held screen out i reckon. The touch screen on the ds is good but i wouldn't trade my psp for ds. I find that ds is to be marketed to smaller kids. but thats my opinion.
Newahys there are lots of really kool games comign out on psp, they jsut took a while. Oh and the game sharing feature is very good too, no lagg there, i did it with tekken 5 dark ressurection.
So in conclusion Ds is good but for me psp is better

hope this helps, leave questions n i will see if i can answer them