The benefit of the + is that I don’t have to set up anything in advance. I can type an email address on any device, including devices I don’t own, and still have it work as an alias.

I do have a “real” email alias as well that I use for true spam (e.g. to get “customer club” discounts while everything they send me is autoredirected to spam by a mail filter). I reserve the + addresses for things I want in my inbox, but still want to be able to filter easily in my mail client.