psp games are great, nds games might be godly then =)
psp games, i can tell u that, out of 10 games, 7 is crap, 3 is decent. out of the 3, 2 is originally jap, 1 is eng. out of the 2 jap, only 1 is availble in english.
good side is, FULL colour resolution big screen, decent average sound output. versatile.
nds games are much more better, wayyyyyyy better. but they have this similar problem with psp as well, 1/2 of the better games out there are in jap.
there is this mario basket ball perfert! teris also good with its online features, a doctor game where u use the touch screen to operate on your patient!!! alot more innoative. if your into innoative, unique, i suggest NDS. but if you appericate grahip more than gameplay, watching movies psp is for you.
but nds pricing should be only slight cheaper than psp, unless u got chopped ( pricing including memory cards, 3rd party stuff to support homebrew application)
basically, what psp can do, nds could do too, but only which is better.
personally what i have is psp. i do regret, but if i can travel back, i will neither get psp or ndsl