i have both psp and ds.

i can tell u that ds has more innovative games such as osu tatakae ouendan (or elite beat agents us ver) and some nice remake of rpg classics such as final fantasy iv. other unusual games such as cooking mama, nintendogs, etc.

psp on the other hand, if u have ps3, u can use it for remote play. can listen to mp3s, watch movies, surf the net using the built-in browser, listen to internet radio. have good games such as patapon, ffvii crisis core to name a few.

if u think graphic matters not, i suggest the ds.

otherwise, u want it to be fully loaded with features, its the psp.