Hi wendym,
I changed your username to wendym because wendy was already in use. I hope that’s OK. I also moved your posts and my replies to a new topic of it’s own so that our conversation wouldn’t get mixed in with another member’s topic.
The benefits of higher quality/density materials would be that they will be more durable and have a longer useful life than lower quality/density materials. The support of a mattress is a function of its design not the durability of the materials inside it.
There is more about primary or “deep” support and secondary or “surface” support and their relationship to firmness and pressure relief and the “roles” of different layers in a mattress in post #2 here and in post #4 here that may also be helpful in clarifying the difference between “support” and “pressure relief” and “feel”. These are all separate issues from the quality and durability of the materials inside the mattress.
There is more about the most reliable ways to choose a mattress that is the most suitable "match for you in terms of PPP (Posture and alignment, Pressure relief, and Personal preferences) either locally or online in post #2 here that can help you make the best possible choice and help you identify and minimize the risks involved in making a choice that turns out not to be as suitable as you hoped for but when you can’t test a mattress in person then the most reliable source of guidance is always a more detailed conversation with a knowledgeable and experienced retailer or manufacturer who can help “talk you through” the options they have available based on the information you provide them, any local testing you have done, and the “averages” of other customers that are similar to you. They will know more about “matching” their specific mattress designs to different body types, sleeping positions, and preferences and which of the firmness and layering options they have available will have the best chance of success than anyone else.
Since the top layer in all the mattresses you are considering is latex the motion transfer would probably be similar in all of them although it may be slightly better with the Alexis but they will have more personal experience with all the different mattresses they manufacture so they would be a more reliable source of guidance about any smaller motion transfer differences between them than I would.
If you rearrange the layers in the Alexis (using the firmer latex layer on top) then of course there wouldn’t be any extra cost but if you exchange one of the layers for a softer or firmer version then there is a minimal cost involved for the exchange (see post #7 here). The same mattress is also available from Brooklyn Bedding if you call them directly (although they don’t list it on their site any longer since they introduced their new mattress) and if you purchase it from them then the trial period would be 120 days and the cost of a layer exchange would be a flat $75.
The Dreamfoam Natural and the Brooklyn Bedding #BestMattressEver and the Aloe Alexis all use high quality materials that would be suitable for your weight range so you are certainly looking at some great quality/value choices. Once you are down to finalists that are all choices between “good and good” and none of them have any obvious weak links or lower quality materials in their design and if there are no clear winners between them then you are in the fortunate position that any of them would likely be a suitable choice and post #2 here can help you make a final choice based on your material preferences (the type and blend of latex layers you would prefer), your conversations with each of them, their prices, the return/exchange options they have, any additional extras that are part of each purchase, and on “informed best judgement” based on all the other objective, subjective, and intangible parts of your personal value equation that are most important to you.
Phoenix