Hi Khacken,
Just in case you haven’t read it yet … the first place I would start is the mattress shopping tutorial here which has all the basic information, steps, and guidelines that you will need to make the best possible choices and comparisons between mattresses.
There is more about the different ways that one mattress can match or approximate another one in post #9 here. All the layers and components in a mattress will affect the feel and performance of all the other layers and components above or below it and the mattress “as a whole” so the only way that you can really know whether one mattress will match another one is if both mattresses the same type of materials in the same thickness and firmness levels and have the same or a very similar cover. These types of comparisons can be very complex and difficult if you are using specs as a reference point as soon as there are any differences in the design or specs of two mattresses in any of the layers because even small differences in design in any of the layers or components can sometimes make a surprising difference in how well a mattress compares to another one or how well it will match your specific needs and preferences in terms of PPP (Posture and alignment, Pressure relief, and Personal preferences).
There are really only two ways to either choose a mattress or compare two mattresses. The first of these is based on your own careful and objective testing using the testing guidelines in the tutorial post.
If you can’t test a mattress in person then the “next best” approach is a more detailed conversation on the phone with a knowledgeable and experienced online retailer or manufacturer (such as SleepEZ) where you can provide them with more information about the specifics of the mattresses you have tested and done well with (including the type and blend of latex in each layer and the thickness and ILD of each layer and the type of cover) along with more information about you and your body type and sleeping positions so they can help “talk you through” which of the options they have available will have the best chance of success (see mattress firmness/comfort levels in post #2 here). They will know more about their own mattresses and “matching” them to different body types, sleeping positions, and preferences based on “averages” than anyone else because they do this every day. In the case of an online purchase … the return and exchange options (either for a mattress or individual layers) you have after a purchase can also be an important part of lowering risk and the “value” of your purchase if you aren’t certain about how well a mattress will work for you so you can use your own personal sleeping experience to replace local testing and decide whether the options you choose in your initial configuration and combination of layers is working well for you so if it isn’t you still have good options available to do some fine tuning by rearranging or exchanging layers.
Phoenix