Hi Kozyrox,
This is partly true because properties like comfort/pressure relief and support/alignment are quite subjective and are also relative to each person depending on body type and sleeping style along with physiology, health conditions and many other variables. The other part of this though is that Sealy doesn’t disclose the quality/density of the materials in their mattresses which is the single biggest factor in durability and how quickly foam layers will soften and break down and without this you can’t make any quality or value comparisons with other mattresses (which of course is the biggest reason this information isn’t disclosed).
You are in a somewhat difficult position similar to other members of the forum that found us after they had purchased a major brand mattress or purchased from a chain store and when they needed to exchange it they had discovered that there really weren’t any mattresses available that were particularly good choices.
Post #2 here includes links to several of these threads with information, comments and suggestions that you may find helpful to make the best of a bad situation when you are considering an exchange where good choices are either limited or non existent.
Careful testing along the lines of the links in post #1 here has the best odds of determining the balance betwen pressure relief and alignment which is best for your back because there are to many variables and unknowns for anyone to use “theory at a distance” to make comfort choices for someone else … particularly when a manufacturer doesn’t provide any meaningful information about their mattresses.
Thicker layers of memory foam aren’t necessarily “bad” because it depends on the body type and sleeping style of each person and on the specific type of memory foam in the mattress but because memory foam becomes softer in response to heat, humidity, and the length of time it is compressed … it can be tricky in thicker layers because you may be in good alignment when you first go to bed but as the memory foam becomes softer over the course of the night you can wake up out of neutral alignment (where the heavier parts of the body and in particular the hips/pelvis have sunk into the mattress too far).
As you can see in some of the links in the “read first” post I linked … none of the major manufacturers provide meaningful information about their mattresses that allow consumers to make informed buying decisions or for the salespeople or consumers to have any idea of the quality or value of what they are selling or buying. These are mattresses sold by marketing stories not by meaningful information about the quality of the materials and this is the reason I suggest avoiding major brands and chain stores completely in the guidelines.
You can read a little more about the different models in the Sealy Optimum line in post #48 here to give you an idea of how they compare to each other in terms of design and construction based on the information I have been able to find.
Phoenix