Hi Mika80,
I think the first place I would start is the mattress shopping tutorial here which has all the basic information, steps, and guidelines that can help you make the best possible choice … and know how and why to avoid the worst ones (which includes the major brands and any mattress where you aren’t able to find out the quality of the materials inside it). I would also avoid the major chain stores such as Sleepy’s (see the guidelines here).
There is also more in post #13 here about the most importat parts of the “value” of a mattress purchase.
The only way to know whether another mattress is comparable would be if you can find out the type and quality of all the materials in this mattress (see this article) and then find another mattress that used exactly the same type and quality of materials and had the same design which would be unlikely.
Outside of the quality of the materials … the only way to find a mattress that would be similar in terms of PPP (Posture and alignment, Pressure relief, and Personal preferences) would be based on your own personal testing and subjective perceptions.
I would probably “reset” how you are looking for a mattress and follow the steps in the tutorial post because buying a mattress without knowing anything about the quality of the materials inside it is one of the most common reasons for buyers remorse much too quickly after a purchase.
Phoenix