Hi mopeede,
there are basically three types of foam used in mattresses which are memory foam (gel foam is a type of memory foam), polyurethane foam, and latex. Of the three, memory foam is the warmest, polyurethane is next, and latex is the coolest of the foams.
There are many variations in each type of foam but memory foam by it’s nature will be warmer because the cells are more densely packed and with less resilient foams that “absorb” more energy and don’t “bounce back” like more resilient foams … mechanical energy is turned to some degree into heat energy. Some of the newer generation memory foams and gel memory foam are “less warm” but still not as breathable or cool as most polyfoam or latex.
There are also many factors besides just the foams used that can influence sleeping temperature and some of them are mentioned in post #2 here. Some of the ways that are being used to cool down memory foam are discussed in Post #6 here.
So to some degree has tried to sell you a bill of goods. Gel memory foam is a step in a better direction but is only one piece of the puzzle and there is more hype than substance in the stories that are attached to it. Flippable mattresses are also widely available but not generally in the chain stores or with major brands who tend to use less expensive materials and sell them at higher prices. The reason that pillowtops and eurotops often break down is because of the use of lower density/quality polyfoam in the upper layers. If a pillowtop or eurotop had latex or higher quality foam … they wouldn’t have these common issues to nearly the same degree.
If you read the overviews in the “mattresses” section of the site it will give you some basic information that will help you ask better questions and also help you know when someone is “educating” you or “selling” you.
There is a longer article here about the pros and cons of latex and it is one of the highest quality mattress materials available but each person has their own unique needs and preferences so there is no “should and shouldn’t” in terms of materials . … only preferences
I would suggest first reading this article which will help you avoid most of the worst choices and hopefully keep you away from major brands and chain stores and other mass market outlets where you will tend to hear these types of “stories”.
There are some good choices in Alberta and if you are in Edmonton post #136 here may help and if you are in Calgary … then post #2 here may help. two of our manufacturing members are there and like all the members here carry great quality and value mattresses and would be the first place I would visit.
If you are somewhere else in Alberta … let me know.
Phoenix