Hi jodiesattva.
Many manufacturers make a wide range of mattresses that can vary from lower quality and less durable materials to higher quality and more durable materials in a wide range of prices. In the case of Flex while the price may be lower compared to their usual selling price, I’d still advise caution when you’re purchasing something without knowing the makeup of the materials within the mattress, The price point would obviously be another part of your personal value equation. While durability may be for a shorter time, you’ll still want to make sure that whatever you choose uses good quality and durable materials as you’ll want as consistent of a comfort life during the time you’ll be using the mattress, and there are many lower-quality materials that can initially feel good but only have a comfort life of just a few years. If you are able to find out the specs in the mattress then the guidelines I would suggest to make sure there are no lower quality materials or “weak links” in a mattress you are considering are in this article and there is more detailed information yet about the many factors that can affect durability and the useful life of a mattress relative to different people in post #4 here and the posts it links to.
All things being equal outside of whether a mattress is a good match for you in terms of PPP … a mattress is only as good as the quality of the materials inside. As you established that both mattresses feel comfortable to you, I would choose based on durability (useful life) criteria. At a glance…on the one hand, Contour has high-quality materials with no known weak links …. on the other hand Flex is less expensive but of unknown materials… additionally, from your description, you seem to indicate that you are valuing the “stability” of the Flex mattress. While I can certainly help with “how” to choose … It’s not possible to make specific suggestions or recommendations for either of the mattresses because the first “rule” of mattress shopping is to always remember that everyone has a different personal value equation with different priorities and what is important to them, may not be important to others and that there are too many unknowns, variables, and personal preferences for anyone else to make the appropriate choice. With this in mind, I suggest that you revisit and reassess what is important to you based on your personal value equation.
You would need to make sure that each of the mattresses meets the minimum quality/durability guidelines relative to your BMI. Your BMI is based on your height and weight. You can use one of many online BMI calculators such as here) to find it. Then, you’d just want to be sure that the memory foam was a higher density of 5lb/ft[sup]3[/sup] or more (which in the case of Contour is), and that the memory foam layers are not too thick and that the support structure and other foams were appropriate for higher BMI individuals.(Which in the case of the Contour the 2" lb/ft[sup]3[/sup] the polyfoam in the support base would also be a good and durable),…either way the Contour would have good and durable materials for your weight range.
I hope this brings some clarity and I’d be interested to learn of your eventual decision.
Phoenix