The PSP is really nothing but a portable PS1.5, and you can go and check the attach rate for the PSP vs DS. Very low attach rate for the PSP, that is very few games are sold vs the number of PSPs sold, because most people use it as a portable emulator and multimedia device! Some even install OSes like Windows and Linux on it!!!
The PSP is a powerful platform, but it isn't what a handheld should be. The DS has loads of good games, there are plenty of JRPGs and platformers, and a lot of them make use of the stylus and mic. Plus the huge amount of fun, multiplayer party games, or as you might call them minigames
We can agree on one thing, that is to disagree