Hi cartman,
None of your questions have any “absolute” or definitive answers because there are too many variables involved and all of these mattresses are “apples to oranges” comparisons. There is also no formula that can predict which mattress may provide you with the best pressure relief or support that is more accurate than your own personal experience. I would also question the real life benefits of this type of detailed “engineering analysis” when it won’t answer the real question which is which mattress will provide the best PPP (Pressure relief, Posture and alignment, and Personal preferences) over the short and long term. The choice between them would be more about your personal preferences, your confidence that one will be more or less suitable for you, your options if it’s not, and on all the other factors, tradeoffs, and benefits that are part of each person’s personal value equation that that are most important to them.
My role is to help eliminate the worst choices and help you reach a point where your final choices are between “good and good” and you have reached this point. Beyond this my job is to step out of the way and give you some guidelines about how to choose rather than “what” to choose or the type of technical analysis that would take many hours of analysis and thought with very few real life benefits. You are really past the point of “better and worse” because none of the mattresses you are looking at have any weak links in terms of quality and durability would not be a significant issue with any of them. Durability is also relative to each person because long before foam or other components break down completely they will soften or degrade to the point where the mattress may no longer be suitable or keep you in your “range” of needs and preferences when it would still work perfectly well for someone else for many more years (see post #3 here for more about relative durability). If for example you choose a mattress that is “on the edge” of being too soft in either the comfort or support layers then even a relatively small amount of softening may put you over your line while someone else would still be fine. In other words … your comfort choice will play as big a role in the durability of a mattress and how long it may last for you as the quality of the materials.
If you are looking for the most durable materials and this is the most important factor for you then latex would be on top followed by 5 lb or higher memory foam but this doesn’t take into account what is above and below each layer or whether the most durable material or the design of the mattress will be suitable for your comfort or support needs and other preferences.
In other words … final choices are more about preferences and tradeoffs and your confidence that a mattress will be suitable for you in both the short and long term (or if its not how close it is and what your “fine tuning” options are from that point). Local testing that is done objectively and accurately has the best odds of success (as long as you aren’t just testing for “subjective comfort”) or of making an initial choice that is “close” enough that fine tuning will take you the rest of the way there but some of the online choices also have the option of making comfort or support changes based on your own personal experience which of course lowers the risk involved with an online purchase that makes these options available.
Again … the only “better or worse” is the degree to which a mattress provides you with the PPP (Pressure relief, Posture and alignment, and Personal preferences) that you need and of course knowing the quality of the materials so you have a reasonable assurance that the PPP you need and prefer will last (which you do). Only you can know whether a mattress “works” for you because there is no formula that can accurately predict this that is more accurate than your own experience.
The differences in material type in all these mattresses is also a matter of preference not “better or worse”. Latex, memory foam, and combinations of the two all have a very different “feel” and performance but one is not better than another even though many people may strongly prefer one over the other or even though one may be more durable than another.
Perhaps most of all though … I would keep in mind that when you look back on your mattress purchase the thing you will remember most is how well you slept (or didn’t) over the years no matter how important the other factors are when you are making your purchase.
Once you are down to final choices … technical analysis plays a very secondary role to your needs and preferences and your own confidence that your final choice will be the best match for your personal value equation.
As you can see in post #2 here questions about “which is better” or “which would be my best choice” are among the most common questions on the forum but are also the ones that nobody else can answer with any specificity beyond pointing out any weak links to eliminate and making sure that each person is taking all the many objective, subjective, and intangible factors into account that may be important to them initially or over long term use.
With the choices you have available … it would be difficult to make a “mistake” in terms of quality or value and the only real way to answer which is 'best" for you is to ask yourself which one you believe has the best chance of providing you with all your needs and preferences that are the most important to you in both the short and long term (see post #2 here).
Phoenix