Hi Jezo,
Both of these two manufacturers are knowledgeable but their mattresses are constructed quite differently and take two paths to similar goals (the goal being a mattress that provides a customer with their needs and preferences). Both would have similar durability because the upper layers affect durability more than the lower layers and in both cases the upper layers are latex. This would also depend on the type of latex used in each and on the firmness of the latex in the upper layers (different types of latex have durability differences and the firmness/softness of latex also affects durability). There is more about the many factors that can affect how long a mattress may last for any particular person in post #2 here. Durability in other words is partly about the materials used and partly relative to the person.
Besides the differences in materials … they also use a different method to provide the combination of softness/firmness in the comfort and support layers that can “match” each different person. Of course latex is also a more expensive material than polyfoam. The thicker the latex layers on top … the more “latex like” the overall mattress will be because the “feel” of the deeper layers comes through less than layers that are closer to the surface.
From a “commodity” point of view you could compare the materials themselves in terms of thickness (comparing latex to latex and factoring in the different cost or benefits of different types of latex) and then add in a “value” for any other layers or components that are used (such as additional polyfoam, differences in cover/quilting materials, a foundation or other additions etc).
All of this though would miss the most important point which is which mattress provides you with the best possible PPP (Pressure relief, Posture and alignment, and Personal preferences) and other benefits (including the benefits of dealing with either manufacturer). While either one may be able to provide you with what you need in a mattress (pressure relief and support/alignment) … they would be different in their overall feel and each manufacturer has a different design theory as to the combinations of materials and layering they prefer to use and which they believe provides the best “value” to their customers.
Once you have tested both (and both would be better value than the mainstream mattresses that most people end up buying) … then it becomes a matter of comparing the benefits of each (along the lines of post #2 here) and asking yourself if any cost, material, expected durability, or other differences in each justifies any differences in cost based on your own personal preferences.
It’s like apples and oranges. Some may prefer apples and others oranges and to compare them you would need to first compare the benefits that are applicable to all fruit (nutrients, taste etc) which is like pressure relief, support, and your other preferences. You couldn’t really compare them in terms of “value” (except by some arbitrary method such as vitamin C content or “crunchiness” etc) and to know their value you would need to compare the oranges to other oranges and the apples to other apples with some overlap between them. If you just don’t like oranges then no matter what the relative value of the particular oranges may be … the apples would “win out” in a comparison regardless of the “value” of the oranges.
The latex mattresses at The Mattress Factory would be more similar to the Southerland mattresses here which use varying thicknesses of latex over polyfoam support layers. Of course the quality of the polyfoam will also make a difference in their “value”.
The ones at Magic sleeper would be more of a “traditional” layering that used all latex with a firmer support core and softer comfort layers on top (varying ILD more than layer thickness).
Both of these could make good choices IMO but the first step would be to test each to see how well they “fit” your overall needs and preferences and then to compare their differences (including cost) in terms of their importance to you.
Phoenix