there is no way to predict the long term support of either platform. Blazor has more support now, than I would have guessed. Who knows what browser technology will be popular in the coming years.
Depending on your app design there may be performance differences. Blazor uses a virtual dom (similar to react), Angular an incremental dom. Typescript is not truly type safe while Blazor is. angular can directly access the dom, Blazor uses js interop.
I still pick react/javascipt over Blazor because there is much less boiler plate code, and code is often simpler. Also there is a larger pool of 3rd party components. I would pick Blazor over angular anytime (but that is just me).
also, is it a single page web app or a website? for a website I'd probably recommend razor pages and javascript.