For iOS I'm using Ejecta for quite some time now since memory management was implemented.
As far as phonegap goes, it is the more optimal solution since Ejecta (same as CocoonJS) is not a real browser engine and thus has some limitations.
Phonegap is currently recommended for iOS 8.0+ devices due to the poor performance of the older version's browsers.
It's up to you to test your app and see if your app performs better with phonegap and if limiting yourself to iOS8 is worth it.