It's more complicated when you have many types of item and not many of each item, because a filter inserter can do five types and a splitter can do one.

And if you add some wires, you can have each inserter automatically grab whatever is directly in front of it that isn't on a blacklist. At that point a max-throughput build with inserters is a big but roughly fixed size, while a build for splitters is proportional to the number of items.