The look of the mattress is not always the best way of deciding whether or not the mattress is right for you. You do need to try them to guage the feel before you buy.
Most beds are available in firm, medium and soft ratings but these labels can vary from brand to brand. Comfort is very subjective. There are no universal standards of firmness in common usage in the UK.
Your main aim is to achieve good "posture" in bed. Too soft and your body will slouch - often leading to back pain - and too firm and you will cause discomfort at pressure points such as your hips and shoulder. Ideally the mattress should mould to the shape of your body while remaining supportive. When you lie on your side your spine should be horizontal and you should be able to turn easily.
We would consider this mattress to be medium/firm. However, the firmess will vary depending on the type of base it is on. If you have a solid base the mattress will feel more firm than on a sprung base.