Hi Erion929,
Both of the manufacturers you are looking at have good knowledge and experience and neither of them have any weak links in their design or construction. The choice between Talalay and Dunlop is also a preference choice (see post #7 here) and there is more about the different types and blends of latex in post #6 here. Synthetic Dunlop will also be a little less elastic and a little less supportive than natural Dunlop which is why the firmness choices for each for some people may be different.
The material you are looking at with mattresses 24/7 is most likely blended Talalay (see my reply here in the other thread).
Density numbers with synthetic or blended Talalay and Dunlop are also very different and can’t be compared to each other (synthetic latex is less dense than natural latex so it will be firmer in lower densities).
When you can’t test a mattress in person for PPP and you are dealing with a knowledgeable and experienced manufacturer like Spindle or retailer like mattresses 24/7 then your more detailed conversations with each of them (preferably on the phone or with a live chat) is the most effective way to choose which of their mattresses would have the highest odds of success (see mattress firmness/comfort levels in post #2 here). They will know more about the options they have available and which combination of materials may be the best match for you than anyone else. Any exchange or return policy they offer may also be an important part of your personal value equation so that you are comfortable with the options you have after a purchase if the choice you make doesn’t work out as well as you and the retailer/manufacturer hoped.
Once you have eliminated your worst options and you are down to final choices between “good and good” (see post #2 here) and if there are no clear winners between them, then it’s time for me to step out of the way so that you can make a final decision based on your conversations with each of them, your confidence in each choice, and all the objective, subjective, and intangible parts of your personal value equation that are most important to you along with your “best judgement” or sometimes even just “gut feel”.
You have done some good research and you are in a great position where there are really no “mistakes” in terms of quality or value and while I’m happy to help with “how” to choose … when there are no weak links or “cautions” about any of your options then only you can make the final choice about “what” to choose that is “best for you”.
Phoenix