Hi HoosierLife,
There wouldn’t be any meaningful benefit in terms of durability but there would be some differences between how they feel and perform. Unfortunately you are the only one who can feel what you feel on a mattress and when you are considering two mattresses that have different designs or thicknesses then the only way to reliable way answer these types of questions would be based on your own actual testing or personal experience in side by side testing. Some people would notice a significant difference and others may only notice very little difference or no difference at all.
Each person can have a very different experience on the same mattress so for one person there may not be enough of a difference to justify any additional cost while someone else may have a very different experience on the same mattress and the additional cost would be worth it. In some cases it can also mean that they would be noticeably different from each other but that neither one would be “better” than the other and both would be equally suitable in terms of PPP (Posture and alignment, Pressure relief, and Personal preferences).
I can help describe the properties that are affected with greater thickness (which is in the post I linked) but there is no way for anyone else to predict how this will “translate” into the personal experience of any particular person or how much difference any particular person would notice between them.
This is all part of the process and uncertainty of buying a mattress that you can’t try in person before you purchase it which is why the conversations you have with each manufacturer and the options you have after a purchase to make changes to the comfort and support of a mattress either by rearranging or exchanging layers can be a more important part of the “value” of an online purchase.
There is more about the different ways to choose a mattress (either locally or online) that is the most suitable “match” for your specific needs and preferences and how to identify and minimize the risks of making a choice that doesn’t turn out as well as you hoped for that are involved in each of them in post #2 here.
Phoenix