I have little interest in mobile development, though I can see myself having to delve into it in full force in the future. Thus far, I've been able to steer clear of it. That said, if I had to, I would go with the one where there were the most employment opportunities. Right now, it seems that's React Native. Also, the carry over between React and React Native opens the employment scope up a bit more. But if you're in it for the enjoyment, try both and see what you like.