Originally from Japan, futons are basically big cushions filled with fluffed-up fibre.
Futons must be kept well-ventilated and fluffed up to be comfortable, and because fibres can absorb moisture, futons need to be turned regularly to avoid mildew. Larger sizes can be quite heavy.
Because of their hardness they don't adapt to your body shape and are better suited to small lightly built people.
They provide good full body support without pressure points. Good waterbeds have a bladder design that minimises water movement which causes partner disturbance.
Polyurethane Foam Mattresses
Polyurethane foam comes in a great variety of grades. Cheap low-grade foam mattresses are only suitable for the spare room. High grade foam mattresses provide great comfort and longevity but are hard to find in Australia.
Latex mattresses (natural rubber mattresses) are expensive and also need a flexible-slat base. High quality latex mattresses can be expected to last 20-25 years. If you can't afford a latex mattress, a latex overlay (used over a firm mattress) is a good, comfortable option.
Memory Foam Mattresses
Memory foam (also known as visco elastic foam),was developed about 30 years ago. It is made from polyurethane like traditional foam, but has a different cell structure, which makes it less 'springy' and slower to recover.
Most visco elastic mattresses are made from a layer of visco elastic material adhered to traditional foam. Visco elastic overlays are also available. The thicker the visco-elastic layer, the more you sink in, and the more difficult it is to move, especially heavy folk.