I've found - you become an app developer or you become a web developer. JS can be used for mobile with React Native, Cordova, etc... for quick and dirty apps - sure - but why take the short cut? If you want to be an app developer, learn the native languages (swift for iOS / java for Android) and get ahead of the curve. Ask any Android developer; ask any iOS developer. The differences UI wise keep getting wider and wider that most times, it's really not worth it to get 1 app to do both well. You'll always get the best quality with native. Again - quick and dirty / get it out the door - go for isomorphic. A quality app the maybe wins a design award? Has an isomorphic ever won one?
edit - not saying most of us are out to win awards - give me a functional app over a pretty app any day (if i can have both, awesome) but function always trumps aesthetics. Look at hacker news - by modern design standards, it's downright ugly - but it does it's job (disseminate programmer / IT news) and it does it damn well. None of the stack exchange websites are "OMG what a great looking site" - but they get the job done well. These examples are websites obviously, but the same can be applied to apps. And you get the best function with native.