Hi vade11,
The choice between latex and polyfoam comfort layers would primarily be a preference choice but the only way to know for certain which one you tend to prefer will be based on your own actual testing or personal experience. As you know the 12 in 1 customizable also has many ways to customize the mattress while the Ultimate Dreams latex is a finished mattress that doesn’t provide the option to change the firmness of the comfort layers after a purchase. They also have a Eurotop version which allows you to exchange the firmness of the latex comfort layer which may also be worth considering although the cost is higher. If you purchase either one of them from the Dreamfoam site then you would have the benefit of the additional 10% discount (compared to Amazon) and you would also have the benefit of their 45 day comfort trial as well so the “worst case” risk of choosing a mattress that didn’t work well for you would be the $99 return fee.
There is more about the different types of support systems that are suitable for different types of mattresses in the foundation post here that may be helpful. Some of the wire grid platform/foundations are a low cost choice that may be worth considering.
Phoenix