wire data and ui on browser or send processed page

I'm confused about where to use what. Suppose I am making an webapp than I have two way of making it dynamic.

First:- Send everything(data and how to make ui or say content of UI) in form of json response by making api and than using angular to display it.

Second:- Whatever language I was using to make API I can also use that language to create dynamic page and than send that as HTML with no further processing required.

There are mainly 2 things in any webapp data and UI.

Suppose I have a app with 5 views. Every view has different type of content than every type has different way to represent content and than base on those options for "A" is decided than on base of every options of "A" option to "B" is decided and so on and forth.

Than What should I use for what?