Oh god, surely you don't expect me to learn? I'm too busy building yet another Todo app as a service, I don't have time to LEARN!
Perhaps the one exception, where I take a strong stance on choosing one over the other is Bower vs npm. Use npm. Virtually anything on Bower is already on npm, and npm has better conflict resolution regarding versions. Why use one package manager to install another package manager to use packages that the former can handle on its own? npm, Inc is doing a great job at being THE package manager for frontend too. npm quite simply is superior, in my opinion.
It's okay to forego the latest and greatest. I still use Angular 1.x even for new projects. Why? Because it's not EOL yet. It's still getting updates regularly. When the Angular Team EOL's it I'll reassess, just as I'd do with anything else.
Examine new frameworks and libraries to learn just enough about the core concepts and paradigms they introduce or espouse. Doing so should take no more than an afternoon or two of your time. Then, while you're still building your Angular 1.x app and a client says "I want a React app!" you can discuss the prospect with the confidence of your fundamental understanding of what React brings to the table, and how it builds upon or differs from Angular.