The double chaise sectional exists with or without mattress. Both have their advantages and disadvantages. For the model with mattress, you must be very careful because it will not always be of the best quality, or will not correspond to your needs. Its padding should be your reference. Foam mattresses are very light and cost much less.
Although they are easy to transport, they are not very resistant. If you can afford it, choose a latex mattress. It is dimensionally stable and warmer compared to other materials. The sofa bed without mattress, meanwhile, has a coating that can be fabric, leather or imitation leather. You can add a sofa cover over it that you can customize as you please.
However, this model does not include a storage box. Finally, considering its practicality, the sofa bed is rather affordable. The fact that it exists in several models also means a good price range. In any case, whatever model you choose, it will always fulfill its two main functions. Other furniture, such as a coffee table, should not be heavy to move easily when deploying the sofa bed; they must respect a minimum distance that does not hinder the opening of the convertible sofa.