The two-step wins in one specific situation: the page is already indexed and still carries something worth handling carefully, traffic landing on it, backlinks or internal links pointing at it, or content you want out of search before the URL itself disappears. When a page is genuinely dead weight, no traffic, no links, nothing to preserve, you just delete it and let it return a 404 or 410, which is the right tool for a clean kill. The sequencing only earns its slowness when there is something to lose by cutting abruptly.
Deleting outright is a hard cut. The URL goes dead immediately, anyone arriving from a search result hits a 404, and any link equity pointing at the page snaps with nowhere to go. For a page that mattered, that is an abrupt dead end at the worst moment, while the page is still listed and still sending people. The two-step softens the exit. You add noindex first, which keeps the URL live and working while telling Google to drop it from results on the next crawl. The page quietly leaves search while still functioning for anyone mid-visit. Once it is delisted and you have moved what needed moving, redirected the traffic, repointed the links, you take the URL down. It is gone, but it left on managed terms instead of vanishing under people’s feet.
That is the whole difference, and it is why the two are not interchangeable. Delete is for pages with nothing to wind down, and the staged exit is for an indexed page with standing you want to retire gracefully.
One caveat keeps you from over-engineering it. If the page has a good replacement to send people to, a 301 redirect usually does the job better than the noindex step, because the redirect both drops the old URL from results over time and passes its equity to the target. Reserve “noindex, then remove” for when there is no sensible redirect target but the page still has traffic, links, or search presence you would rather not sever in one stroke.