Hi ergopower,
Even the types of material are strictly a personal preference. There are people who strongly prefer comfort layers that use latex, memory foam, polyfoam, or natural fibers (or any other materials used in comfort layers) and others who don’t like the same materials at all. The same is true of support layers such as innersprings, latex, or polyfoam. All of these are personal preferences.
The only common denominator is that no matter which materials you prefer that it’s high quality, good value, and suitable for your specific needs and preferences. More than that is really a matter of knowing which materials and components you prefer because one isn’t “better” than another for any specific person or circumstances unless it’s a personal preference.
If you are testing mattresses locally I would tend to avoid ILD information because it’s a “comfort spec” not a “quality spec” and it’s only one of many factors that is involved in the perceived softness or firmness of a mattress (see post #2 here). ILD is also not directly comparable between different materials or even different types of latex and with many materials (including innersprings, memory foam, or fibers) ILD information is not relevant or available anyway. Careful and objective testing for PPP and the “feedback” from your body will tell you what you need to know about whether a mattress is firm enough in the support layers and soft/firm enough in the comfort layers to keep you in good alignment and relieve pressure in all your sleeping positions. ILD will generally do more to confuse or in many cases lead to “paralysis by analysis” than it will help when you are testing mattresses locally and I would stick with knowing the “quality” specs of a mattress instead of “comfort specs” (which may not be available in many cases anyway).
Phoenix