Hi tigerpants,
That’s a very broad question that could take many books to answer.
Different mattress designs that have different features and options including using different types of latex, different layer thickesses, a different number of layers, different firmness levels for each layer, different covers and quilting materials, and overall different designs are how manufacturers make mattresses that are suitable for different body types, sleeping styles, and personal preferences.
If you are interested in some of the “art and science” of mattress theory and design and the differences between different types of mattress construction then there is more generic information about different types of layering in the “putting the layers together” section of the site, more about matching mattresses to different body types and sleeping positions in the “your sleeping style, preferences, and statistics” section of the site and in the tips and tricks page here.
There is also more about primary support, secondary support, and their relationship with pressure relief in post #4 here and post #2 here, and more about some of the different specifications that can affect the outcome of a mattress design in post #2 here that may help you “imagine” the effects of different types of layering although there are so many variables involved that the only way to confirm whether any design is a good match for you is your own personal testing (using the testing guidelines in the tutorial post) or your actual sleeping experience.
There is also more about the pros and cons of thicker mattresses in post #14 here and more about the potential benefits of having more individual layers in post #2 here and the differences between having two 3" layers vs a single 6" layer in post #2 here.
It would most likely be a combination of many reasons that are part of the design of the mattress and one of these could be different types or blends of latex yes.
In some designs I did (such as relatively soft comfort layers over very firm support layers where you feel too much of the firmness of the deeper layer or with thinner mattresses that compress from softer to firmer more quickly) and with others that were more suitable for my specific needs and preferences I didn’t.
Arizona Premium and SleepEZ both use Radium Talalay but there is more about blended Talalay vs 100% natural Talalay in post #2 here. 100% natural Talalay in the same ILD will tend to be denser and more “supportive” while blended Talalay can be a little more pressure relieving so this may be part of the reason for your experience.
I think that it’s much simpler to just recognize that “this mattress seems to be a better match for me than that mattress” because it can be a very complex process to learn enough about all the many variables that are part of mattress materials, theory, and design to be able to reliably figure out “why” one mattress feels different from another with all the complexities that can be involved.
Phoenix