There are plenty of great games on the PSP, Last game I beaten on the system was Silent Hill Shattered Memories and it was just, wow.
Oh, you can also "Transfar" PW with the PSP and the trophies earned on the PSP will carry over. Great way to kill time say, waiting for the bus.
I dunno man, the Vita is pretty fun so far, and the library isn't bad at all. It really depends if you like gaming on the go. I love that I could play MGS1, 2 and 3 when I'm waiting to pick up mother at the mall, or when I'm in line in the bank, DMV etc.
I was at the post office playing the Vita and a 40 something year old due went to me and said "Is that Metal Gear 3? WOW!" The guy told me he left gaming since he got married, and he had no idea portable systems could run one of his favorite games. He was just in awe.
I just wonder if I'd look lame carrying a PSP around when the Vita is out . Unfortunately, I don't have a lot PSP games aside from MGS Acid, Portable Ops, and the DGN.
But, I think I might have to pick up a PS Vita before I get a PS4.