Hi dchuck,
This is one of those subjective questions that nobody can really answer for someone else. It would depend on the person and their body type, sleeping positions, and individual perceptions and sensitivities. With a softer 2" comfort layer over a firmer core some people would sink in more deeply or feel more of the firmness of the base layer with 2" of softer latex and may call the mattress firmer because they were more sensitive to the deeper layers. Others may sink in less or would be more sensitive to the top layer and would call it softer. It would certainly have a different “feel” with softer over firmer and a bigger differential between the two layers.
Assuming the latex and the covers are both the same or close equivalents … then the main difference (assuming you have access to all three 3" layers) is you would have more flexibility to customize the mattress in terms of PPP either before or after a purchase by re-arranging or exchanging three layers. Whether this was an important issue would depend on whether one was a significantly better “match” than the other for a particular person. If the two 3" layers in the base were not accessible then assuming that the two core layers could be chosen independently in different firmness levels then they would allow for more ability to customize the mattress before a purchase. For example with the same comfort layer … 3" of 32 over 3" of 36 ILD in the bottom of the mattress would be firmer and could provide more “support” than a single 6" layer of 32 ILD would be softer and could provide more pressure relief than a single 6" layer of 36 ILD.
The two ways to choose a mattress in terms of PPP is either with your own personal testing on a mattress that is the same (or very close) or more detailed conversations with a manufacturer or retailer that can help you choose the option that has the highest chance of success based on your experiences in combination with the “averages” of their customers that are similar to you (see mattress firmness/comfort levels in post #2 here). I would also keep in mind that outside of any differences in materials … the Essence allows for an exchange of the comfort layer while the Adjustable Ultra plush allows for the exchange of the support layer so they are each different in what can be customized and in the options they make available.
Just like any two businesses that offer similar (but not the same) products … differences in their raw material or component costs, different production costs, different business costs, different business models and margins, the cost of different options they have available before or after a purchase, different pricing policies, different shipping costs, and any of the other normal differences between any two businesses will all lead to differences in how each business prices its products. Some products may be more or less costly at one business while others may be more or less costly at the other. Since nobody except the business itself has access to this type of information … there is really no way to answer this except theoretically.
Phoenix