So I just saw this appeared as a Vita only game in the PSN EU store yesterday - ACE COMBAT™ Joint Assault + DLC. I already own the Vita compatible PSP game from 2010, but the store page is incredibly vague about what this release (which is marked as Vita only, not PSP) contains. Is it just the PSP game + some bonus stuff for the PS3 free to play game, or is it an updated release for the Vita with higher resolution graphics and stuff like that?

The single parapgraph description does imply that the DLC isn't actually for Joint Assault, but just "bonus fuel" (the energy currency) for the free to play Ace Combat Infinity, which currently is PS3 only:

This is a bundle including ACE COMBAT™ Joint Assault full game and ACE COMBAT™ Infinity DLC. We offer you 5 Units of Stocked Fuel on the first free-to-play of the franchise.

There isn't even any mention of this release on the Project Aces or Namco Bandai twitter feeds.

I liked the PSP game well enough that I'd consider purchasing an updated version for the Vita, but I wouldn't want to pay for another copy of the PSP version (also, what's up with the other PSP Ace Combat game - Skies of Deception not being available at all on PSN?).