Hi KrazyPanda,
Unfortunately you are the only one that can feel what you feel on a mattress and there are too many unknowns, variables, and personal preferences involved to be able to predict with any certainty which combination of layers will be the best match for you in terms of PPP (Posture and alignment, Pressure relief, and Personal preferences) based on specs (either yours or a mattress) or “theory at a distance”. When you can’t test a mattress in person then the most reliable source of guidance is always a more detailed conversation with a knowledgeable and experienced retailer or manufacturer (such as Mattresses.net) who can help “talk you through” the options they have available based on the information you provide them, any local testing you have done (assuming you know the firmness of all the layers in the mattresses you have tested which may not always be possible to find out), and the “averages” of other customers that are similar to you (see mattress firmness/comfort levels in post #2 here).
There is also more about the different ways to choose a mattress (online or locally) and how to minimize the risks involved in each of them in post #2 here.
There is also more about some of the differences between a latex/polyfoam hybrid and an all latex mattress in post #2 here.
The thickness of a mattress has very little to do with its durability since durability depends on the construction of the mattress and the type and quality of the materials inside it. There is more about the many variables that can affect the durability and useful life of a mattress relative to different people in post #2 here and the posts it links to.
Neither of the two mattresses you are considering would have any weak links in their design.
There is more about the most important parts of the “value” of a mattress purchase in post #13 here that can help you make more meaningful comparisons between mattresses.
When you are down to finalists that have eliminated all your less desirable choices (either in terms of suitability, durability, or value) and you are down to choices that are between “good and good” and there are no clear winners between them then you are in the fortunate position that any one of them would probably be a good choice for you and your final choice (see post #2 here) will really come down to “best judgement” based on all the objective, subjective, and intangible parts of your personal value equation that are most important to you.
As you know I think very highly of Arizona Premium and they are a member of the site which means that I believe they compete well with the best in the industry in terms of their quality, value, service, and transparency.
Only you can decide whether you wish to include any other options in your research or if you are satisfied with the options you have already considered but if you do decide to look at others then the tutorial post includes several links to lists of the better online options I’m aware of (in the optional online step) and post #276 here also includes a list of the factory direct manufacturers I’m aware of in Quebec as well.
Phoenix