The answer is simple and consists of two questions:
1. How stable is the entity behind what you are going to learn? (Protip: Google and Apple are going to be around for a bit longer than most loosely associated groups of hipster developers)
2. Which of the choices has the most answered questions online (yes, probably on stackoverflow)?
(1) can alternatively be written as 'how stable is the framework/language you are learning?'
(2) can also be seen as 'Which of the choices has the most supportive and/or largest community?'
They boil down to the same, though.
My advice: do it native. Android and iOS devving is really quite easy if you don't want to do anything fancy and do it properly. If you do want to do anything fancy, you're going to have to go pretty deep anyway and hybrid frameworks are just going to get in your way.
I (single handedly) spent about 5-6 months creating a PHP backend and a native Android app, whilst the specs were changing. I had to design and implement the structure of the app and that of the backend, etc. I've started working on the iOS version 1 month ago and it is about done (maybe two more weeks). Mind you: this is not because iOS development is easier than Android development (they both have their quirks), but already having a stable backend and a proven structure of the app code allows me to basically translate the Android code to Objective C without much thinking. The core issues in the system design have already been dealt with. It's just implementing a stable design based on stable specs, which we all know is the easiest part of software development.