It's totally worth it for Persona 4: Golden. Persona 4 was probably the best JRPG I've ever played, very solid game play, great story, amazing characters, music and art, and the Vita version only adds more to what was an already great game. c:
If you already have those games, then no. You shouldn't buy a system for games that are essentially director's cuts. However if want other reasons to buy it, there's Zero Escape: Virtue's Last Reward, Little Big Planet PS Vita, and Rayman Origins (again if you don't have it on other systems).