Hi bmbsqd7,
I don’t think there is any way to compare two different mattresses that use different foams and have different designs to the degree of specificity you are looking for. In most cases these types of comparisons are somewhat subjective and only a “approximation” based on a combination of the overall feel, pressure relief, and support of a mattress and are a way to give people a reasonably accurate idea of how the mattress will feel and perform using a widely known mattress as a reference point. Only your own experience can make these kind of assessments to the degree of accuracy you are looking for though.
In cases where your needs and preferences are in a fairly narrow range … then your recourse with an online purchase may become one of the most important parts of your personal value equation if the mattress is outside the range of what you specifically need or prefer (no matter how close it may be for someone else or even a majority of other people).
In this case … you would probably be wise to make sure the mattress was fulfilled by Amazon so you could return it should you need to (although their large item return policy can still be costly) or to choose a mattress that can be either adjusted or changed after a purchase through exchanging the mattress or an individual layer or choosing a mattress that has a return policy that will cost you little to nothing if you need to return it (such as their Cool Series here).
Because only your own personal experience can really answer these types of questions (and everything else is more of a “best guess” based on their experience and knowledge of “averages”) … an online purchase generally needs to include your confidence that you are making a suitable choice, your risk tolerance if you make a mistake, and the “value” of your options if you make a choice that isn’t suitable for you.
For most people it would be “close enough” but this wouldn’t be the case for every person because there are so many variables and unknowns involved in different body types, sleeping styles, physiology, and mattress designs and materials … all of which could affect how closely one mattress matched another in your actual personal experience. these types of comparisons are as much an art as a science.
Phoenix