One big advantage is simplicity: you eliminate the need for a lot of client side technology, such as routing, and push everything back to the server. Also, by

One big advantage is simplicity: you eliminate the need for a lot of client side technology, such as routing, and push everything back to the server. Also, by eliminating application javascript, it allows you to spend more time in your preferred language on the back end. The downside is the same as regular HTML, although less pronounced: since you are driving application state through hypermedia (HATEOAS), the less coarse-grained your state or UI gets the more annoying things are going to be. There are some patterns that help but eventually, if you want to update 12 different places in your UI at once on every keystroke, the hypermedia approach just isn't going to cut it.