I like futons for sleeping on, but not the ones that convert to couches. Ikea has a couch/chaise combo that converts to a bed that we may get for our guest room.
For my preference as a guest, I voted for real bed or Murphy bed, because my back is miserable after sleeping on a bad bed, and most convertible couches and day bed/trundles I’ve slept on have been awful.
As the host, I want something practical but also comfortable to sleep on. So, I may get something other than the two I voted for, but only if I’m convinced the particular item will be good to sleep on.