I tried thoroughly both solutions (for iOS), and in the end I decided to go with PhoneGap, as painful as it sounds.
Sadly both appmobi and cocoonjs doesn't support vital features of iOS (GameCenter, iAds and iAP) which can make a real difference in sales. As far as my experience goes, both solutions are good for amateurish games, if you want to package something vaguely professional you need to have the whole DOM at your fingertips and access to native features. Not even considering that with both of them you'll be battling with missing features or not working plugins (like spritefonts which are pretty vital). Also cocoonjs and appmobi are closed source and services depending on external infrastructure that may not exists in the future.
While both of them give a great performance boost they are not even remotely close to native performance which is a thing that has to be considered, if you want complete freedom you need to go native (or Stencyl).
This will be the last game I'll do with construct2 for mobile, I'm sorry but the technology isn't there by a long shot. Win8 is great, desktop is great but mobile lacks too many features and neither of those solutions are enough to cover the technology hole, that until WebGL gets integrated into webviews.
I say this because the time I lost testing those platform, optimizing the code I could've done a way better game with another engine, think about what you are doing really really carefully to avoid investing time and resources only to see an unplayable mess as a result.