Hi mchesney,
While I don’t have any personal experience sleeping on their mattress … you can see some thoughts about them in post #2 here and in post #19 here.
Unfortunately here is no “standard” definition or consensus of opinion for firmness ratings and different manufacturers can rate their mattresses very differently than others. Different people can also have very different perceptions of firmness and softness compared to others as well and a mattress that is firm for one can feel like “medium” for someone else or even “soft” for someone else depending on their body type, sleeping style, physiology, their frame of reference based on what they are used to, and their individual sensitivity and perceptions. This is all relative and is as much an art as a science. There are also different types of firmness and softness that different people may be sensitive to that can affect how they “rate” a mattress (see post #15 here).
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 that has your best interests at heart and 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 or sometimes to other mattresses that they are aware of that you may be familiar with than anyone else.
The choice between different materials or different types of mattresses is a preference choice not a “better/worse” choice (assuming that both use good quality and durable versions of the material you prefer). There is more about the pros and cons of latex vs memory foam in post #2 here but the best way to know which of them you tend to prefer would be based on your own personal experience.
Phoenix