Hi rcy1,
The closest comparison between FSF with 3 layers of Dunlop to the Spindle mattresses would be to their 10" Abscond that used their 100% natural Dunlop layers but this would also be a somewhat apples to oranges comparison because FSF has a wool quilted cover while the standard Spindle version uses a cover that is quilted with polyfoam and the cover can be a significant part of the cost (and performance) of a mattress. There would also be some difference between the “feel” of the Mountaintop 100% natural Dunlop that Spindle uses which is made with a continuous pour method and the molded Dunlop that FSF uses although they are very comparable in terms of quality. Spindle also has a wool quilted cover option which isn’t on their website yet (NOTE: they now use wool quilting along with 100% natural Dunlop in their mattresses) which would make the comparison a little closer. The ILD’s may also not be completely comparable because Mountaintop uses a different method for testing ILD although Neal would likely be able to tell you which of his layers would be closest to the ILD’s or density of the FSF Dunlop. He may not have something comparable to the firmest versions at FSF but again you would need to talk with him.
When you aren’t able to test a mattress in person then the only way to answer these types of questions (outside of the quality of the materials which you can compare based on knowing the type and blend of the latex) would be with more detailed conversations with the manufacturer. Just to add to the mix of similar options SleepEz also has a similar design with 3" of 100% natural Dunlop (molded) with a wool quilted cover.
Once you are comparing apples to apples then you can make more meaningful comparisons between them. Of course it may also be well worth considering Spindle’s synthetic latex which is a lower cost version of latex than the 100% natural but while it’s also a good quality material and has great value, its feel and performance is also different and 100% natural Dunlop would be denser, more resilient and “supportive” compared to its synthetic counterpart. Once you have talked with each of them (and tested the ones that you can) then which of your final choices would be “best for you” would depend on the parts of your personal value equation that are most important to you.
You are certainly be choosing between “good and good” no matter which one you decide on.
Phoenix