Hi domiagnew,
Unfortunately your question is much more complex and subjective than you may realize (or would have hoped for).
There is more about the different ways that one mattress can “match” or approximate another one in post #9 here.
ILD by itself is also only one of several factors that can affect the firmness/softness of a material (see post #4 here).
There are also different types of softness/firmness that different people can be more or less sensitive to (see post #15 here) all of which will have a different effect on the overall “feel” of a mattress (which is very subjective) and even different people can have very different opinions about how two mattresses compare.
In addition to this … the ILD ratings of Mountaintop foam are different from the ILD ratings of most molded Dunlop manufacturers and while the subjective “feel” of synthetic continuous pour Dunlop is similar to other types of Dunlop … the ILD ratings are only relatively close to other continuous pour Dunlop blends that are made by Mountaintop foam because of differences between how their ILD is tested and rated compared to other Dunlop latex manufacturers. They have a 40% ILD range and a 25% ILD range and based on feedback from some manufacturers I have talked with the bottom end of the 40% ILD range would probably be the closest to other types of latex. Their 25% ILD range is listed here (I don’t know the 40% ILD numbers).
What all of this “translates” into is that if there are more than minor differences between the designs or type of materials in two mattresses then the only way to know how similar or different they would feel to you would be based on your own personal testing or experience.
I would ask Dreamfoam whether the ILD numbers they provided are the 25% or 40% ILD ratings or if they are comparable to other types of latex in their experience and if they confirm that they are (they are familiar with other types and blends of latex) then you could use them to compare their mattress in very approximate terms to other Dunlop mattresses that used a similar thicknesses and firmness for the layers in the top 6" or so of the mattress.
Phoenix