An extra-firm mattress is generally NOT suitable for side sleepers and is often considered the worst choice for this position. This type of mattress can lead to two significant issues:

1. Pressure Point Pain: An extra-firm mattress exerts substantial pressure on your body, particularly on your shoulder joint and the prominent area of your hip.

2. Spinal Misalignment: To alleviate this pressure, your body may naturally shift positions. You might end up sleeping with your arm tucked under your body or with your hips rolled forward, which can cause your spine to twist and move out of its neutral, straight alignment.

A plush mattress has a soft top layer that relieves pressure and a firm core that lets side sleepers sink in a bit. In contrast, a firm mattress feels hard and barely sinks, making it better for stomach and back sleepers who need strong spinal support.

The key difference between a firm mattress and an extra-firm mattress is the level of cushioning. While both offer strong support, an extra-firm mattress has little to no cushioning, creating a rigid, "on top of the bed" feel.

A pillow-top plush mattress has a soft, thick pad sewn on top, giving it a cloud-like feel and letting you sink in more. A Euro-top plush mattress has similar padding, but it is sewn to the mattress edges, which makes it look neater and provides firmer edge support.