PSP hands down
Their is much more potential in the system. Its a universal multimedia system with Internet, movies, music, and games.
And Monster Hunter Freedom 2 rocks. I have it myself.
And if you like RPGs their is a ton on PSP. Monster Hunter 1, 2 and 2G, Valhalla Knights 1 and 2, Final Fantasy Crisis Core and a whole lot more. And their is lots of racing, sports and shooters on top.