Here’s what John Mueller from Google said about 404 and 410.
“From our point of view, in the mid term/long term, a 404 is the same as a 410 for us. So in both of these cases, we drop those URLs from our index.
We generally reduce crawling a little bit of those URLs so that we don’t spend too much time crawling things that we know don’t exist.
The subtle difference here is that a 410 will sometimes fall out a little bit faster than a 404. But usually, we’re talking on the order of a couple days or so.
So if you’re just removing content naturally, then that’s perfectly fine to use either one. If you’ve already removed this content long ago, then it’s already not indexed so it doesn’t matter for us if you use a 404 or 410.”