Hi ikonos,
Your choices are not quite “apples to apples” and hopefully I can do some justice to the differences between them that may be important to you in making your decision.
Organic Dunlop vs 100% natural Dunlop:
The word “organic” is used in many ways in various descriptions on the internet and has many shades of meaning besides the technically correct use of the word. In general it is used to describe a mattress that uses more organic materials than another mattress that uses materials that may be completely natural but not certified as organic. In some cases … materials that are not certified as organic may actually be superior and more “pure” and offer better quality or value than those that are certified as organic. An example of this is Pure Grow wool which is not certified organic but uses organic farming methods that are superior to many “organic” alternatives. They just haven’t had these methods certified. Even local food products may use organic farming methods that are better than products that have the organic certification but have not been “certified” by a certifying agency because of the extra cost that the certification adds to the product regardless of quality.
In the case of Dunlop latex … the certification is for the raw latex and certifies that the raw latex itself and farming methods used to produce the raw latex are organic. This means that the main raw material (but not the only one) used to make a latex core is certified. The core itself though is not certified as organic (each separate product from raw material to finished product and the methods used at every step along the way to produce them need to be certified in order to be “technically” labelled as USDA certified organic). Dunlop latex cores that use all NR (natural rubber) and no SBR (synthetic rubber) are still only in the low to mid 90’s in terms of percentage of rubber that is used (there are other materials needed to make the raw latex into foam) so the core itself is not certified organic even though the raw latex in it is. Even if there was an organic certification available for a latex core (which there currently isn’t) and a mattress used all certified latex cores and certified organic covers that used certified organic cotton and wool … the mattress itself wouldn’t have an organic certification so it couldn’t be technically labelled as “organic”.
EDIT: There is now an organic latex certification called GOLS (Global Organic Latex Standard) and several manufacturers (CoCo latex, Latex Green, and Arpico) manufacture certified organic Dunlop latex cores (see post #2 here). You can also read more about the different “levels” of organic certifications in post #2 here
Of course this level of detail becomes overwhelmingly complex so in most cases the manufacturers use the word descriptively more than technically.
The main benefit of a latex core that uses certified organic raw latex (and there are three companies that produce this (Latex Green, CoCo latex, and Arpico) is that the raw material and farming methods used to produce the latex have been certified. The certification has little to do with any difference in quality or performance between 100% natural Dunlop and Dunlop where the natural rubber used is certified organic. For some people this added level of cost for a “certified” material may have some value and for others … the fact that both are 100% natural is good enough and the extra cost of the certification isn’t worth it.
For a manufacturer that offers Dunlop though that uses certified raw latex … this means that the latex layers they use will be more expensive than those that only use 100% natural latex. Some manufacturers know that many consumers are attracted to the organic “label” to various degrees and the added cost of the latex layers are worth it because they attract people who “buy organic” regardless of any real difference in materials and the extra expense and they believe that the extra expense of these materials and the extra customers it brings them are worth the tradeoff of the customers they may lose because of the extra cost and higher prices this involves. Of course there are also many mattress descriptions that completely confuse 100% natural and “certified organic” and in this case they would use orgaic in a different context meaning “it’s natural”. This is where specific questions can be valuable for those who want to know exactly what is technically “organic” and what is just natural.
All of this (the importance of the “organic” certification and label) and the actual level that this certification involves (raw material, latex layer, or the whole mattress itself) is part of each person’s “value equation”. I personally would hesitate to pay for an organic certification that added to the cost of what I was buying when I wasn’t convinced that it provided any meaningful benefit over another product that was only “100% natural” but equally “pure” but that is only my personal “value equation”.
Certified Oeko-Tex:
This is very different from an organic certification and involves testing the material for harmful subtances and offgassing. All Talalay latex (blended or natural) is Oeko-Tex certified and all the higher quality Dunlop is also certified by Oeko-Tex or another equally reputable certifying agency such as LGA or Eco-Institut. This is a “safety” certification rather than an “organic” certification. If a mattress has high quality latex fom a reputable manufacturer … then safety is not an issue.
Both manufacturers offer this so this would be a “wash”
Both manufacturers likely use the same suppliers (Latex Green and/or Latexco) although I don’t know this for certain and both would likely have the ability to hand pick a specific density level variation within a range. Because there is a wide variance across the surface of a Dunlop core though regardless of density … details that are this fine are questionable in terms of value. A 1 kg difference in density is very unlikely to be within the perception range of anyone and the ILD consistency across the surface of the layer itself would be much larger than this anyway regardless of the density chosen. IMO … this may be getting to levels of “analysis” that are mostly meaningless. There is value though in lying on a local mattress that is a little too firm or soft and having the manufacturer make adjustments to change it with the benefit of knowing exactly what you are lying on and which direction you need to go and which layer to change.
Again … the choices of customizing the layers would be similar between them although SleepEz also offers the ability to add Talalay to the mix (which may or may not be important to someone). The advantage of doing this locally is that you can actually test the differences to see what you can feel and what you can’t.
I would assume that this means that the latex doesn’t have voids or other “imperfections that have been patched” but I don’t know for sure.
With their 8" special … you have the choice to add Talalay which is a personal preference between materials that have a different feel and properties. If you prefer Talalay over Dunlop then for you this would be a “value added” choice in the same way that if you prefer “organic” over “100% natural” then for you this would be a “value added” choice.
The SleepEz special also uses 2 x 3" layers instead of a single 6" core which for some people offers more flexibility in terms of the combination of the core layers they can use. This added “flexibility” of the properties of the core layers (for example using M/F would be different from a 6" layer of either medium or firm) may also be important to some and if it was it would offer another “value added” option. For an online purchase a more “fine tuned” customization after purchase may be more important for some but one is not any “better” than another in terms of quality. For someone where a single core or the ability to choose it’s firmness level is all they really need then the added flexibility of two layers would have less value and not be an issue.
If I said this somewhere then it was not accurate. If you have the link to the post that says this then I should correct it. There are other members here that do offer a similar mattress with a single 6" core and a separate comfort layer but SleepEz is not one of them.
The cotton/rayon stretch knit cover is a very attractive choice for many people and there have been comments that it is one of the nicest covers they have seen. Rayon (or other cellulosic or viscose fibers such as bamboo, eucalyptus and other “artificial” fabrics) are very popular and for some they are a preference over a cotton ticking. Bamboo for example is strong, breathable, and has a very nice hand feel which is one of the reasons it is so popular. Both would make good choices although and again … for some the “completely natural” benefit of cotton may be a preference over anything that uses natural raw materials (like the different types of viscose fibers) but are processed and turned into a fabric in “less than natural” ways.
I personally believe that Dunlop ILD’s are “approximations” because of the variations throughout the material and because of the limitations of an ILD measurement itself which is only measured at a specific percentage of compression (usually 25%). If a supplier uses them accurately (and each manufacturer of course knows how they order their material) then of course this has it’s advantages as well even if it sometimes creates a tendency for consumers to make comparisons that are based on a belief that the ILD’s are more accurate in real life than they really are or to make comparisons that end up being different from what they expected. ILD’s in Talalay are more consistent but even they are in a “range”. In the end … the expertise of a manufacturer themselves and their knowledge of the materials they use can be much more valuable than only using ILD’s as a basis of comparison between different mattresses or materials.
This is another “value added” benefit that would be more important to some than others. For those who like latex pillows … it would certainly be a bonus.
If this “approximates” your testing … and you are OK with or prefer the differences between Talalay and Dunlop in the comfort layer … then these would be good choices IMO.
I personally believe that local testing and purchase has a “premium” attached to it and I personally pay more for the “accuracy” and lowered risk of a local purchase. When this “premium” is more than about 20% or so though … then the benefits of an online purchase may take on greater “value” which offsets any additional risk. Of course the risk is also affected by the flexibility, ease, and cost of any exchanges that are offered. Each person may place a different level of importance on different things and the level of either real or perceived risk tolerance may be different but this is part of each person’s value equation. In this case as well … part of the difficulty is that the most meaningful comparison would be with similar materials but if the “organic” materials are not as important to you … then the lower cost of 100% natural may be more important to you and a manufacturer that offers this as a way to bring down the cost may increase their value even if the actual comparison is not based on the cost of the materials themselves.
Hopefully this has “explained” most or all of the differences between them and gives you the “tools” to weigh all the tradeoffs that are involved in making your “best” decision. I always feel great when people are down to making final choices that are comparing “good with good” rather than “better with worse” and you are certainly in this position. Final choices can be the most difficult of all especially for those where there are many factors that they are considering besides just price but if you eliminate the differences that are less important to you and focus on the ones that are the most important … one difference at a time you will end up with the best choice for you.
If I’ve missed anything … feel free to post with more questions 
Phoenix