I bought the 219 to apply shadow under the eye, but it's too big for my eyes in that area and puts down product lower than I want. I wind up doing a lot of cleanup with a Qtip. So these days I use it only to apply a shimmery color on the inner corner or do an outer v and blend out with another brush. Mine isn't as "pointed" as others I've seen in YT videos so maybe that's why I don't like it as much as others like theirs.
I use the 231 all the time for applying shadows & pigments to the lower lashline and it works great for me. I wouldn't say it's a necessity though, I picked mine up because I got it for a good price at the CCO.