Hi menelaus7,
Welcome to the Mattress Forum! 
Actually, I teach that it comes down to a few more things than that which I outline in the mattress shopping tutorial here. The key is to learn about the componentry first within a mattress and judge the level of quality, and then follow the steps outlined in the rest of the tutorial. Two of the most important links in the tutorial that I would especially make sure you’ve read are post #2 here which has more about the different ways to choose a suitable mattress (either locally or online) that is the best “match” for you in terms of “comfort”, firmness, and PPP that can help you assess and minimize the risks of making a choice that doesn’t turn out as well as you hoped for and post #13 here which has more about the most important parts of the “value” of a mattress purchase which can help you make more meaningful quality/value comparisons between mattresses in terms of suitability (how well you will sleep), durability (how long you will sleep well), and the overall value of a mattress compared to your other finalists based on all the parts of your personal value equation (your “preference”, as you mentioned earlier) that are most important to you (including the price of course and the options you have available after a purchase if your choice doesn’t turn out as well as you hoped for).
Outside of PPP (which is the most important part of “value”), the next most important part of the value of a mattress purchase is durability which is all about how long you will sleep well on a mattress. This is the part of your research that you can’t see or “feel” and assessing the durability and useful life of a mattress depends on knowing the specifics of its construction and the type and quality of the materials inside it regardless of the name of the manufacturer on the label or how a mattress feels in a showroom or when it is relatively new so I would always make sure that you find out information listed here so you can compare the quality of the materials and components to the durability guidelines here to make sure there are no lower quality materials or weak links in a mattress that would be a cause for concern relative to the durability and useful life of a mattress before making any purchase.
In its simplest form … choosing the “best possible” mattress for any particular person really comes down to FIRST finding a few knowledgeable and transparent retailers and/or manufacturers (either locally or online) that sell the types of mattresses that you are most interested in that are in a budget range you are comfortable with and that you have confirmed will provide you with the all the information you need about the materials and components inside the mattresses they sell so you will be able to make informed choices and meaningful comparisons between mattresses and then …
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Careful testing (hopefully using the testing guidelines in the tutorial) to make sure that a mattress is a good match for you in terms of “comfort”, firmness, and PPP … and/or that you are comfortable with the options you have available to return, exchange, or “fine tune” the mattress and any costs involved if you can’t test a mattress in person or aren’t confident that your mattress is a suitable choice.
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Checking to make sure that there are no lower quality materials or weak links in a mattress you are considering relative to your weight/BMI range that could compromise the durability and useful life of the mattress.
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Comparing your finalists for “value” based on #1 and #2 and all the other parts of your personal value equation that are most important to you.
Based upon your earlier comments of your wife being eco-conscious and leaning toward an all-latex bed, I’m surprised you’re considering this mattress, as it doesn’t use latex foam at all.
You may wish to read this thread and the links contained therein for more information explaining how there is no such thing as “natural” memory foam. You may also wish to learn a bit more about Essentia and some of their history by doing a forum search on them here . While some of their mattresses use higher quality materials, I certainly wouldn’t treat the information on their website (or on some of the other websites I’ve seen that write about them either) as a reliable source of “fact based” information and I would also make some very careful “value” comparisons before considering any Essentia mattress because they do tend to be in a higher budget range than other mattresses that use similar materials.
When you’re not able to test out a product in person, investigating and becoming fully informed of any potential return/exchange program would be an important part of your personal value equation. Foam Sweet Foam does allow for a layer swap out in their 60 day comfort exchange, and they do offer a 120 night trial. Both programs charge for the return shipping. The Essentia 60 day money back guarantee allows for a return les a 9% transportation fee. This applies only to purchases made directly with Essentia.
Foam Sweet Foam is a member of this site which means that I think very highly of them and that I believe that they compete well with the best in the industry in terms of their quality, value, service, knowledge, and transparency. They are extremely knowledgeable about latex and different configurations, and I wouldn’t hesitate to recommend them for your consideration.
I think you are referring to the fact that there is some Dunlop latex that is certified organic (Global Organic Latex Standard, or GOLS), but that there is no Talalay latex with the GOLS certification. The other part of your questions refers to whether a piece of latex foam is 100% natural (NR), blended of natural and synthetic (NR/SBR), 100% synthetic (SBR). For a Dunlop latex to be GOLS certified, it would be the 100% NR version.
Most people that are looking for a “natural” mattress are usually concerned more with “safety” than whether the materials have an actual organic certification. There is more information about the three different levels of organic certifications in post #2 here and some of the benefits of an organic certification in post #3 here and there is more about the different types of organic and safety certifications ( like Oeko-tex, Eco-Institut, Greenguard Gold, C2C, and CertiPUR-US ) in post #2 here and more about some of the differences between organic and safety certifications in post #2 here and there are some comments in post #42 here that can help you decide whether an organic certification is important to you for environmental, social, or personal reasons or whether a “safety” certification is enough. All the latex you are likely to encounter (either Dunlop or Talalay that is made with either natural or synthetic rubber or a blend of both) will have a reliable certification such as Oeko-Tex, Eco-Institut, Greenguard Gold, or C2C and based on actual testing I would consider any type or blend of latex to be a very “safe” material in terms of harmful substances and VOC’s.
If you want to learn more about the difference between SBR and NR rubber, you can read a bit more about that in post #2 here.
I know that’s a lot of information to throw at you, but if you start with the mattress shopping tutorial and read through things as you would a good book, and not trying to memorize everything, it will put you on the track to “resetting” how you go about shopping for a mattress and hopefully making a choice that satisfies everyone in your family.
I look forward to your updates.
Phoenix