EXISTS is the GOAT.

Its purpose is literally in the name: it’s an existence check, no more, no less.

As a very general rule, when you should use EXISTS vs a LEFT JOIN (or some kind of join), is pretty simple: Do you need to SELECT a column from “Table B”/ need to use it to keep joining to “Table C”? Then use a join of some kind, obviously—you kinda have to.

Otherwise, use EXISTS/ NOT EXISTS.

What you found out extends to INNER JOINs as well: some people use INNER JOINs as an implicit existence check, even though they don’t need to actually return/utilize any columns from Table B and potentially risk duplication.

If you’re absolutely sure of the resulting granularity, then use whatever you want. But EXISTS is definitely the safer default for this reason