Functionally (har har) there are a few differences that I can think of, but for many uses they are interchangeable.
Big differences:
Events can be called from console commands (ce, ke), functions can not
Events run in the main event graph, therefore can access timelines, and can use latent nodes, functions can not
Events can be created that connect to delegates, functions can not
Functions can have return values, as far as I’m aware events cannot (although i’ve never tried)
Functions have capability to have local variables, that are only in scope inside that function (and, bonus, it creates local variables that match all the input parameters automatically, which helps keep large blueprints from having lines all over, or making temp variables, as you might with an event)
… if none of those situations apply, they are pretty much interchangeable.
oh, multiplayer probably has some fun dealings with functions vs events, but i haven’t actually done anything multiplayer in a bit over a decade… so… not real sure on what’s up in there these days.