Specialized databases have the advantage of being, well, specialized... For example, a specialized OLAP database which knows about the schema of the data can e

Specialized databases have the advantage of being, well, specialized... For example, a specialized OLAP database which knows about the schema of the data can employ much more streamlined storage and query operators, so it should have a "natural" performance advantage. However, a very specialized database may later lock you in to something, and in case you need something different, you will end up with running multiple different special-purpose databases. Not saying this is necessarily bad (or good), but it is at least one aspect to consider how many different databases to you want to operate & manage in your stack.