Personally I'm of the camp that HTNL schema data should only represent what's visually displayed, much like how accessibility is usually done. In that way I like Microdata because it reinforces that if there isn't a DOM node showing price, for example, I shouldn't be showing that data in a visually hidden way.

For REST, I think the only reason HTML has been useful this long is because of the REST ideas that Fielding gave a name to. Today people just don't use it much, too many sites lean on client side rendering and fetching data from JSON RPC calls that we call REST.

I prefer REST, hell I wish we had proper XSLT 3.0 support for client side rendering logic without JavaScript.

I don't fully understand XSLT, but I've been building something which I believe solves a similar problem (albeit JSON-LD and Javascript). The general XML ecosystem of solutions have always looked really complex to me. You need to understand a lot more types/elements than I think is reasonable for people to author with but they are from before my time. I took a look at XForms 2 and it had its own way of defining functions which on top of the other XML quirks has security concerns.