Hi levander,
There are different types of gel and gel particles that react differently to heat. You can see the different types of "temperature regulating technologies in post #9 here and the end of post #4 here. If you have a solid gel material it would be much more heat conductive (like a marble countertop) than a memory foam which has gel of various types added to it but this type of gel is too firm to be used successfully in thicker layer or without some type of surface modification and is usually found in thinner layers over other types of foam. The type of gel added to other foams can vary and the percentage of gel added can also vary from about 5% to about 30%.
You would find that the “hand feel” of most gel foams will be noticeably cooler than regular memory foam (not to the degree of a countertop though) but that depending on the percentage of gel in the mattress they will equalize over time with body temperature at which point the insulating properties of the foam will become dominant. Depending on the amount and type of gel the temperature regulating effect will last longer or shorter over the course of the night. It may be enough to help someone while they are going to sleep or with a greater percentage of gel it could last for a longer part of the night. The cell structure of the foam will also play a major role because gel added to more closed cell foam will have little or very temporary benefits because there would be no air circulation to remove the heat it absorbs to the environment.
So as new generation gel foams reach the market (currently at 3rd generation) the information is evolving yes. As I mentioned earlier the size of the particulates and how easily they remain embedded in the foam will also make a difference in durability and larger particles will degrade the foam faster because they are larger than the cell walls but smaller particles will embed themselves in the cell walls of the memory foam and be less likely to migrate and abrade the cell walls and have less effect on durability. Most of the newer generation gel foams (either thermally conductive or phase change microparticles that encapsulate the gel) that use particles are moving towards smaller particles for this reason and the ones that Brooklyn Bedding uses (along with others as well) are good quality. I would also bear in mind that there are also advances being made in more open celled memory foam with better ventilating properties.
In very general terms … a gel memory foam will be roughly equivalent in durability terms (possibly slightly less) with the same density memory foam with the exception of 1st generation foams which use larger particles (that migrate out of the foam more easily) which will be less durable.
It’s pretty much impossible to quantify the specific degree of effect that a gel memory foam will have on temperature because the temperature regulating properties of a mattress as a whole will also depend on many other factors besides just the foam (see post #2 here and post #29 here) and also depends on the person (where they are in the “oven to iceberg” range) and the exact composition of the foam which generally isn’t information that any foam manufacturer will provide to the public so you are mostly dependent on the choices and descriptions of a manufacturer who will usually look at and test several gel foams made by different companies before choosing the one they decide will work best in their application and for their criteria to include in their mattresses.
Post #2 here has more information about the different types of gel foams and gel memory foams and as I connect with various “experts” such as foam chemists and new information or foam types comes to light or reaches the market I will add to it.
Select foam also sells gel memory foam toppers that are good quality and they are also in the list of better gel memory foam suppliers in post #4 here along with some of the other members of this site. NOTE ADDED: They are no longer a recommended member of this site … see post #1 here).
Latex and wool toppers would tend to be more ventilating and cooler than memory foam (gel or otherwise) over the course of the night for most people (assuming all the other factors are equal) and some types of more open cell polyfoam may as well (such as quilting foams used in the quilting of the cover) although they may not have the same “hand feel” in terms of temperature as gel memory foam or other types of gel foam materials.
Phoenix