A cracked or uneven ceiling in a room that is already low leaves three realistic choices: tension a stretch membrane just below it, build a new plasterboard ceiling under it, or repair and skim the ceiling you have. They look more alike in a finished room than their marketing suggests, and they differ most in the places you do not see at first: how much height they take, what happens with light fittings, what a leak does, and who can repair them later.
This comparison renders all three in the same room, from the same position, in the same daylight, and then sets out what the evidence does and does not show. It does not crown a winner. Stretch ceilings in particular attract strong claims in both directions; where a claim is measurable, the page says who measured it and for which product, and where nobody has measured it, the page says that instead.
Nothing here replaces a survey of your ceiling, the documents for a specific product, or building control where fire separation is involved.