Hi Cfrivera,
If your mattress was fulfilled by Amazon then I would talk to the large items return department if you need to return a mattress (see post #11 here). Many of their customer service people may not be aware that this is who you need to talk with if you are returning a mattress that was compressed when it was delivered.
There is more about the different ways that one mattress can “approximate” another one in post #9 here but unless all the layers and components in a mattress are the same in both then the only reliable way to know how one mattress would compare to another one would be based on your own side by side testing (with either no or very little time in between because our memories for something as subjective as firmness or the “feel” of a mattress isn’t very long lasting). Even smaller differences between two mattresses can make a surprisingly big difference for some people and when you have two mattresses that use different materials or designs (or the types and blends of latex are different) it’s really not possible to know how they will compare for you unless you compare them in person.
If you are using a flexible support system under a mattress then this would also affect how the mattress would feel in terms of PPP compared to a solid non flexing support system.
If you can’t compare two mattresses in real life … then the only meaningful source of guidance about how two mattresses compare would be talking to a knowledgeable and experienced online retailer or manufacturer who was familiar with the mattress you are using as a reference point and how their own mattresses would compare to it. I would also keep in mind that two mattresses that feel very similar to some people may feel different for others that have a different body type, sleeping positions, or are more sensitive to smaller differences between two mattresses.
I would also be very careful about using one mattress as your ideal “target” because and I would suggest “rating” all the mattresses you test based on a common set of criteria that are part of your personal value equation (see here).
There is also more about the different ways to choose a mattress and how to minimize the risks and uncertainty involved with each of them in post #2 here.
Phoenix