Hi wh200,
Oops … a case of mistaken mattress 
The Ultimate Dreams Latex Ultra Plush currently uses 2.35 lb base foam which is higher density/quality than the 10" gel memory foam mattress uses.
In terms of performance it would depend what you were comparing it to. You can read a bit more about the difference between a latex/polyfoam hybrid and an all latex mattress as an example (latex is a higher performance material than even good quality polyfoam) in post #2 here. Even in the same foam density … there are also many variations in how a foam feels and performs and there are higher and lower performance versions of foams in the same density. “Better performance” would depend on how you define “performance” and which of the many foam properties are most important because this is relative to the design goals of the mattress and how each layer interacts with every other layer and component. Density is more about durability while performance can have many different definitions. For example a very stiff foam with a lower compression modulus that is less costly may be the best choice in some mattress designs while an HR foam which has a wider compression range from soft to firm and is more adaptable to different body types and sleeping positions (closer to latex) may be a better choice in a different mattress design where it was used in a layer that had more effect on how the mattress “feels”.
The closer to the surface a foam layer is the more it will affect what most people “feel” when they lie on a mattress which is mostly about surface feel and pressure relief but the deeper layers and their affect on the support of the mattress and how well it keeps you in a neutral alignment can have a significant effect on how they feel when they wake up in the morning (either with or without back discomfort or pain).
The foam directly under the top layer will affect durability more than the bottom part of the mattress (again depending on how much you “go through” the top layer and compress it) but the foam immediately under the top layer of a mattress and to a lesser degree the deepest layers can also have a significant effect on the overall performance of the mattress and how well it adapts to and matches the needs and preferences of different people. Every layer has an effect on every other layer but the farther apart they are the less two separate layers will affect the performance and “feel” of the other.
Phoenix