Hi Saitta3,
I’m glad you found us … welcome 
Just in case you haven’t read it yet … the first place I would start is the tutorial post here (the first post in this thread) which has all the basic information, steps, and guidelines that can help you make the best possible choices based on the criteria that are most important to you.
I would need to know the specifics of two mattress you are considering to make any meaningful comparisons. They both use similar “raw materials” but have different designs and options.
If you have tested mattresses at Lake Mattress then with a more detailed conversation with Rocky Mountain mattress they would be able to give you more detailed information about how their mattresses compare to the ones you tested and were the best “match” for you and provide good guidance about which of their mattresses would likely be the best choice. They are familiar with the materials and options available at Lake Mattress.
Latex is a great material but it’s certainly not the only material that can provide pressure relief in a mattress. Memory foam, polyfoam, microcoils, natural fibers, buckling column gel, and other materials can also provide good pressure relief depending on the specific design of the mattress. The choice between the “feel” and performance of different materials is really a personal preference.
Outside of making sure there are no obvious weak links in a mattress in terms of durability (and all materials have more or less durable versions) … which mattress is “best for you” (regardless of whether it’s best for someone else) or which retailer or manufacturer that you choose to deal with would really depend on all the objective, subjective, and intangible parts of your “personal value equation” that are most important to you. “Better” is really a matter of which mattress is “best for you”.
If you follow the steps in the tutorial post one at a time you will end up with some great “final choices” that have no “weak links” that will all be good quality and value.
Phoenix