[burntsushi]

> The options and tools for configuring and tweaking relevancy between ES and PostgreSQL's FTS are surprisingly similar for many application use cases.

Maybe in very very limited scenarios, but in general, they aren't even close. PostgreSQL doesn't take corpus frequencies into account, which makes it pretty difficult to come anywhere near the relevance ranking quality of Elasticsearch (or any proper search engine).

In order to tell whether PG vs Elastic is appropriate for your use case, you need to do an evaluation. See: https://en.wikipedia.org/wiki/Text_Retrieval_Conference