Understanding your sleep style is the key to choosing the best mattress for your needs. For example, side sleepers benefit from a soft mattress, while back and stomach sleepers require firmer surfaces for spine support. However, this choice can be complicated if you’re sharing a bed. Many couples have similar body types and favor the same sleep positions, but others do not. If you and your partner have conflicting preferences, you may have to compromise with a medium or medium-firm mattress. Alternatively, you can both be happy with a split king size mattress with different firmnesses.