Hi pressurepts,
Thanks for taking the time to share your comments and “warning” about Select Foam. It’s great to see that your credit card chargeback was successful!
That’s a short question but with a much longer answer 
ILD/IFD is only one of several specs that makes one material feel softer or firmer than another (see post #4 here) and the ILD or IFD of different materials or even different types of the same material often aren’t directly comparable to each other (see post #6 here). The ILD or IFD of a single layer also isn’t particularly meaningful because every layer and component in a mattress (including the cover) will have an effect on the feel and performance of every other layer and component in the mattress and on the mattress “as a whole” and putting too much focus on ILD/IFD alone or any other single specification (especially if it’s only a single layer) will most often be more misleading than helpful.
The ILD/IFD of memory foam can also change with temperature, humidity, and the length of time that the memory foam is continuously compressed (memory foam tends to get softer over the course of the night) and ILD/IFD testing with memory foam also produces different results than ILD/IFD testing on more resilient materials so the ILD/IFD of memory foam can be particularly misleading if you are comparing it to other types of foam.
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 (or vice versa) 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 very subjective 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 as well (see post #15 here).
Unless you have a great deal of knowledge and experience with different types of mattress materials and components and their specs and different layering combinations and mattress designs and how they combine together and can translate them into your own “real life” experience that can be unique to you … I would tend to avoid using complex specs to try and predict how a mattress will feel or perform for you. When you try and choose a mattress based on complex combinations of specs that you may not fully understand or only based on a single spec for a single layer that may not be as relevant or meaningful as you believe it is then the most common outcome is “information overload” and “paralysis by analysis”.
I would always keep in mind that no matter how many specs you know about a mattress or how much you try and “analyze” specs to try and predict how a mattress will feel … the only way to really know how any mattress will feel to you will be based on your own personal testing or your actual sleeping experience.
While other people’s comments about the knowledge and service of a particular business can certainly be very helpful … I would always keep in mind that you are the only one that can feel what you feel on a mattress and I would be cautious about about using other people’s experiences or reviews on a mattress (either positive or negative) or review sites in general as a reliable source of information or guidance about how you will feel on the same mattress or how suitable or how durable a mattress may be for you and in many if not most cases they can be more misleading than helpful because most consumers have little knowledge about mattresses and mattress materials or how to assess the quality and durability of the materials in a mattress and any mattress that would be a perfect choice for one person or even a larger group of people may be completely unsuitable for someone else to sleep on (even if they are in a similar weight range). In other words … reviews in general certainly won’t tell you much if anything about the suitability, quality, durability, or “value” of a mattress for any particular person (see post #13 here).
You can see some general comments about what I call “simplified choice mattresses” in general in post #1 here and you can see some more specific comments about Leesa and Casper along with many of the other “simplified choice” online mattresses in post #2 here in the same topic. A forum search on “Leesa” and on Casper (you can just click the links) will also bring up many more posts with comments and feedback about them as well.
Like any online mattress you won’t be able to make side by side comparisons with other mattresses in “real time” to assess how they compare for you but they all have a very good return policy that lets you test them in your bedroom instead of a showroom with little risk and if they aren’t at least a “good enough” match for you in terms of “comfort”, firmness, and PPP then you can return them for a refund.
I would be cautious with the Leesa because the 2" of 3 lb memory foam in the Leesa is a lower quality/density material than the minimums I would generally suggest in the guidelines here and I would consider it to be a potential weak link in the mattress (although the 2" of Avena polyfoam above the memory foam would improve the durability of the memory foam somewhat compared to having the same lower density memory foam in the top layer of the mattress).
While there are no lower quality materials or weak links in the Casper relative to more average weight ranges (less than the mid 200’s or so) … for most of the members here they probably wouldn’t be the best quality/value choice compared to some of the other simplified choice mattresses that are available.
Outside of the list of the simplified choice mattresses and the local list I linked in one of my earlier replies … the mattress shopping tutorial also includes several other links to lists of many of the better online options I’m aware of (in the optional online step) that include many different types and categories of mattresses (including memory foam mattresses) in a wide range of budgets, firmness levels, and with different return/exchange policies that may also be well worth considering. The online memory foam list also includes a range of memory foam mattresses that may be worth considering and several of them make memory foam mattresses that are designed to be reasonable approximations of many of the Tempurpedic mattresses (including the Rhapsody Luxe).
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 specifics of their mattresses and the properties and “feel” of the materials they are using (fast or slow response, resilience, firmness etc) and the options they have available that may be the best “match” for you based on the information you provide them, any local testing you have done or mattresses you have slept on and liked or other mattresses you are considering that they are familiar with, and the “averages” of other customers that are similar to you. They will know more about “matching” their specific mattress designs and firmness levels to different body types, sleeping positions, and preferences (or to other mattresses that they are familiar with such as the Tempurpedic Rhapsody Luxe) than anyone else.
Phoenix