I have Dragons Crown installed on my 3, and the 5 just shipped so I'm gonna wait for that to see how it runs.
I completely missed the Vita as a system, never so much as touched one. What are your favorite games on it? Bonus points if it's not graphically intense and doesn't take too much power.
The MGS HD collection on any other platform is a better choice. The Vita versions are rather compromised, and MGS3 in particular is a challenge to play. e.g. 30fps, even more awkward controls, and the HD "collection" doesn't even include Peace Walker like how it did on PS3.
That said, playing MG1 and MG2 on the Vita through MGS3 HD is a good experience.