You might be interested to know that since this forum is powered by Discourse, which means you’re using an Ember app right now 
Most of the big frameworks today will ultimately help you achieve the same thing but in different ways. One is not objectively better than the other. And much like learning a programming language, as long as you properly grok one framework it’ll be easier to learn others later if and when you realise your first pick wasn’t quite what you needed.
If you’re having trouble deciding on which framework to learn first, one way to do it could be to browse through the “built with X” sites and try figure out which framework seems to be used most frequently by the type of company or app that you would most like to work with.