Hi packinmn,
I certainly agree with this. Even though both may be “suitable” for a specific person and both can be good “value” … a polyfoam base layer would certainly make a difference in the relative “value” of a mattress or in the ability to make meaningful comparisons between mattresses. I did make some calls to some of the merchants in the Nashville area list very recently when another member mentioned they were having difficulty tracking down an “all latex” mattress in the Nashville area and after asking specific questions about whether they carried any, the results are listed in my comments in post #8 here.
If they are going by the “firness ratings” of Latex International which is the source of their Talalay latex … then “soft” would be 24 ILD and extra firm would be 36 ILD. Medium would be 28 ILD.
Unfortunately there is no way for someone else to give you any meaningful opinions about how a mattress may sleep for any particular individual (in terms of pressure relief and support anyway) that would be more accurate than your own personal testing. If you tested a mattress that was similar to what I am assuming is the Prince here and described how it performed and felt in terms of PPP (Pressure relief, Posture and alignment, and Personal preferences) then I may be able to speculate how a mattress that was similar but had some differences may compare but without a reference point there are just too many variables involved except to say that it would be “in the range” of something that would be suitable for a heavier person. It would depend on how much someone of a specific body type and sleeping positions felt the firmness of the layers below the softer comfort layers (and also on whether the talalay GL was fast or slow response) which would vary from person to person. With 2" of soft Talalay over an inch of medium Talalay over 3" of extra firm Talalay it would feel firmer for example than say the Emperor here which has 4" of “soft” latex over an extra firm Talalay layer. Of course it would be easier to speculate about some of the preferences such as temperature regulation because Talalay is more ventilating and breathable than other types of foam and Talalay GL would be a small improvement over “regular” Talalay here as well but this doesn’t speak to how well it would relieve pressure or provide support for your specific body type and sleeping positions.
The key would be whether the comfort layer was thick and soft enough to provide good pressure relief in all your sleeping positions (along with secondary support that comes from filling in the gaps in your sleeping profile in all your sleeping positions) without being so thick and soft that your heavier parts were sinking down too far to keep you in good alignment.
I wish there was a way to be more accurate but your own testing will be much more accurate than any “theory at a distance” that I could offer.
Phoenix