Hi JoD,
Comfort is a subjective experience that is relative to each person. There are also too many unknowns, variables, and personal preferences involved to be able to predict which mattress would be best or “most comfortable” for someone else based on specs (either yours or a mattress) or theory at a distance (see mattress firmness/comfort levels in post #2 here).
Trying to choose a mattress based on the many different and interacting specs that can affect comfort/pressure relief or alignment/support (or only using ILD which is a small piece of a much larger puzzle) without a reference point based on your own personal experience that can help you “translate” how different combinations of specs “feel” to you in your own real life experience are most likely to lead to “information overload” or “paralysis by analysis”.
There is also more about the different ways to choose a mattress and the risks involved in each (and how to mitigate the risks) in post #2 here.
Latex is a very durable material and isn’t easily damaged in normal use unless you pull or tear it (which doesn’t happen when you are sleeping on it). There are certainly no weak links in either one of the mattresses you are considering.
ILD is not particularly meaningful with memory foam because it changes in response to temperature, humidity, and the length of time it is continuously compressed. Memory foam ILD ratings are not comparable to the ILD ratings of other types of materials because ILD testing for viscoelastic materials produces different numbers than it does for fast response materials. An ILD that would feel “firm” with memory foam (say 18 ILD) would feel soft with other fast response materials.
ILD in latex is not related to the percentage of natural rubber and any type or blend of latex can be made in a wide range of ILD’s. ILD numbers also aren’t comparable between different types of materials or even different types of latex partly because there are different ways to measure ILD (see post #6 here) and partly because ILD itself is only one of several specs that affects how soft or firm a material (or a mattress) will feel to any specific person (see post #4 here).
The torso length for people with different heights are closer than the difference in their heights would otherwise suggest and the zero gravity position would be useful for any height.
There is more about purchasing an adjustable bed in post #3 here and the adjustable bed thread it links to.
There is more about the most important parts of the value of a mattress purchase in post #13 here but since PPP is the most important part of any mattress purchase … if you are considering an online purchase I would focus on your more detailed conversations with each of them so they can use the information you provide them to help “talk you through” which of the options they offer would have the best chance of success. This along with the options you have after a purchase to further customize a mattress or to exchange individual layers or components or the mattress itself or even return it for a refund can reduce the risk of making a choice that doesn’t turn out as well as you hoped for when you can’t test a mattress in person before you purchase it.
Phoenix