Floor model mattresses are similar to used ones since they are technically used. In fact, even more people have probably laid on a floor model than the used one, since many customers visit stores to test out mattresses.
With a floor model, you get more information about the mattress’s construction, materials, and firmness, but it’s still worn down and you can’t guarantee its cleanliness. Also, floor models are normally sold as-is and are final sale, so you won’t be able to return it if it’s not right for you.