Warning: opinion ahead, feel free to ignore.
Leaving aside the issue of what framework to choose, it’s a fundamental truth that web apps run in JavaScript, which means if you’re going to work on them, you have two choices:
- write JavaScript
- find some other language that transpiles to JavaScript, and work in that
If you are coming from Java, chances are you are going to absolutely hate JavaScript. Frankly, if you have any programming background in any language not named JavaScript, chances are you are going to hate JavaScript. TypeScript is a much more comfortable environment for somebody coming from any strongly-typed language, and you will end up much more productive in it, even taking into account the learning curve.
The only people I would not give the advice in the previous paragraph to are those who have been writing JavaScript for 10+ years, and are thoroughly accustomed to it.
The reason I’m laying it out this way is this: if you’re planning to port an existing, running, functional Angular app to Vue simply because you’ve heard that Vue has an easier learning curve than Angular, I would suggest you at least read through the Angular Tour of Heroes and decide if you really think it’s that scary.
Whatever framework you choose to use, learning TypeScript (and, by way of osmosis, some of how JavaScript works under the hood as well) is going to be a bigger task than picking a framework. Having the Angular project as an existing codebase will, IMHO, make learning Angular easier than trying to learn Vue from scratch.
Porting software generally entails having at least rudimentary skills in both environments involved, so you will have to pick up some Angular in order to be able to do the port, unless you’re planning on just reverse-engineering the entire thing from interacting with it, totally ignoring the existing codebase.
So, to answer your direct question, whatever you do, yes TypeScript is going to be worth it. I would still urge you to at least consider sticking with Angular, and make a full evaluation of the pros and cons of doing so versus moving to Vue.
Of course, I guess none of that matters if you were tasked specifically to port this to Vue for some other political reason.