Hi backman,
This would depend entirely on the person and the specifics of the materials inside it and which mattress was the best match for their body type, sleeping positions, and preferences in terms of PPP (Posture and alignment, Pressure relief, and Personal preferenes). You can read a little more about the effect of thickness in post #14 here.
There is more about the most important parts of the “value” of a mattress purchase in post #13 here that can help you make more meaningful comparisons between mattresses. The most important factor will be the suitability of the mattress followed by the durability of the mattress and then how they compare based on all the other parts of your purchase that are most important to you.
The cover and quilting layers of a mattress can certainly have an effect on the feel and performance of a mattress and there is more about the pros and cons of different types quilted covers vs an unquilted knit cover that is more stretchy in post #12 here and the posts it links to.
There is more about the different types and blends of latex in post #6 here. Talalay latex only comes from two different companies and they both make blended latex that is “about” 30% natural and 70% synthetic or 100% natural (although Latex International has just started making Talalay latex that is 100% synthetic). Neither one makes Talalay latex that uses 80% natural and 20% synthetic rubber. I would also be aware that 100% natural latex doesn’t mean that there isn’t anything else in the latex core because no latex core will only contain rubber (see post #18 here).
There is more about the difference between two 3" layers and a single 6" layer of the same type and firmness in post #2 here.
When you are down to finalists that are a choice between “good and good”, none of them have any weak links in terms of durability, and there are no clear winners between them, then your final choice (see post #2 here) will really come down to a matter of “best judgement” based on all the objective, subjective, and even intangible parts of your personal value equation that are most important to you.
Phoenix