There's tons of posts out there explaining "how", but not so much justifying "why" beyond the "oh, it's new, it's cool, just move on".
Consider ex...
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Performance wise, Angular 2 seems to be a lot better than AngularJS. This article shines a light onto the peformance issues that AngularJS has: auth0.com/blog/more-benchmarks-vir...
My personal opinion is that I prefer the way Angular 2 is structured, and I prefer Typescript, also.
It's a good article, but I ask you: Does it matter if one car goes 99mph and another goes 102mph when the street's limit it's 45mph?
Putting in User's perspective: is it relevant if one framework renders in 50 ms while another renders in 35 ms, when User doesn't perceive it?
From the standard user perspective, with good/fast network, maybe it won't really matter. But with people with bad connections, it can make quite a difference. I live in South America, so internet connection here is quite bad. Again, my personal opinion, after working with both, I find Angular 2/4 quite faster than JS on slow connections.
We're in the same fix!