Hi swidrosest, gcrain, and cjwest,
A few comments from scanning your posts …
If you let me know your city or zip I may be able to point you in the direction of some latex that you can test locally.
With higher weights it becomes more important to choose more durable versions of any foam in a mattress … especially in the comfort layers. With higher weights I would consider memory foam (or gel memory foam) that is 5 lbs or higher … especially in the layers that are closer to the surface. With latex I would consider firmer versions (about 28 ILD or higher or at a minimum 24 ILD) because softer latex will be less durable than firmer latex with higher weights, and with polyfoam I would use 1.8 lb density as a good minimum density.
There are other factors involved in the sleeping temperature of your mattress so it may not only be the “foam” that is the reason for sleeping too hot … although some types of memory foam tend to be warmer than the other two types of foam materials (you can read more about the factors involved in sleeping temperature in post #2 here).
Latex is a foam … along with memory foam and polyfoam (the 3 main types of foam). All foams come in a range of softness and firmness levels so it would never be accurate to say one type of foam is softer of firmer than another because they all have different versions. Having said that … memory foam is all in the “soft” range (which is why it isn’t used as a deep support layer) but how it feels can vary widely with conditions.
Memory foam (and gel memory foam) responds according to pressure, heat, humidity, and the length of time it is compressed and its softness and firmness is variable depending on conditions. Latex and polyfoam respond primarily to pressure alone and aren’t “time dependent”. You can read more about how memory foam responds and the many factors that can change how soft or firm it “feels” in different conditions in post #9 here and post #8 here.
You can also read more about comparing memory foam to latex in post #2 here but it’s always best to use your own personal experience because each person may have very different perceptions or describe the differences between then in very different ways.
Higher densities in memory foam are more durable but any density in memory foam can be made with a wide variety of different properties and types of response (see the earlier links in this post). Density is the most significant factor in the durability of memory foam up to about 6 lbs or so and after this the benefits of increased density are diminished. Higher density beyond this point has more of an effect on the feel, response, and compression of the foam. Tempurpedic uses their 7 lb Tempur - HD memory foam in the top layer of the Rhapsody, Allura, and Grandbed and in the second layer (under the 4 lb memory foam) in the Cloud Luxe.
Phoenix