In all seriousness, neither the PSP or DS is superior to its counterpart. They have their strengths and weaknesses afterall, with the PSP having powerful specifications and beautiful games and the DS having a touch screen (innovative gameplay) and fun games, just to name a few.
What makes a handheld system good?
In my opinion, that would be good portability and good battery life. Being a handheld system, developers developed the consoles with portability in mind. If the system has poor portability, it fails as a handheld system. Its like carrying a PS2 around with an small LCD display; it makes no sense.
Likewise, a good battery life defines portability. It makes no sense to carry a "portable" console with 1 hours worth of battery life. You'll end up carrying the charger and extra batteries, ultimately defeating the meaning of "portable".