Which one should I buy? NDS or PSP?

I really want to have a handheld gaming console, but I'm still considering between NDS or PSP... I want to play FF Crisis Core and FF Tactics on PSP, but I also want to play The World Ends with You, Kingdom Hearts 385/2, and FF XII Revenant Wings on NDS.... Which one do you think I should get and why? Thanks, I appreciate all your answer