The spring coils in the hybrid mattress allow much more air flow in the mattress. Air spreads through a mattress - any mattress – and a hybrid mattress will tend to be cooler than a 100% foam mattress. That said, a lot depends on the air flow through the foam. Some mattresses, such as Amerisleep mattresses, possess excellent air flow and cooling properties, although their hybrid equivalents will cool you down more. Also, the hybrid will have more bounce than a 100% foam mattress, so is better for young couples. Also, they are usually more durable than foam mattresses.