I have only the DS with two games, Trauma Center: Under the Knife and Nintendogs Best Friends. But there are easily 20 games that I really want for the system, while the only game I want for the PSP is the new GTA.

I love the DS, and I'll probably get a PSP as well, but not untill I can get the system along with GTA for under $150. So it'll be a long while.