Disclaimer: I haven't delved much into Angular 2, but I know a great deal about React.
I think the question is not so much how is it better in general, but how it's better for your use case. All frameworks have their advantages and disadvantages; but I think as a whole one isn't universally better than another. Some general points for why you would choose a framework though might be:
There are other aspects which people will surely bring up, but from a general sense you can frame your choice with these in mind. Not so much as "This is better than that", but more from a standpoint of why the framework is a good choice at all.
Really though you'll want to explain how it's a good fit for your use case. What are the aspects of your application that lend themselves to a particular framework or methodology? Does the framework fit your particular skill set in some way that makes it easier for you to develop with it? That sort of thing. I think you're better off justifying it that way as opposed to trying to say that Angular 2 is a universally better framework than X or Y.