Hi lpearson,
The three main benefits of the Eurotop are in post #2 here and a little more detailed explanation of the potential benefit for some people of a thicker base layer is in post #39 here.
There wouldn’t be any significant difference in durability but for some people that are heavier there may be a small improvement in comfort although according to Dreamfoam they would feel the same for most people.
Neither one would need a latex topper unless you chose an ILD that was a little too firm and wanted to soften the comfort layers of the mattress (the comfort layer is already latex and is the same in both mattresses).
Latex is the highest quality and longest lasting of all the foams (polyfoam, memory foam, and latex foam) so this isn’t likely to happen for many years but if the upper latex layer does break down sooner than the other layers and the rest of the mattress is still in good condition then you could replace it with a new layer instead of replacing the whole mattress yes.
Phoenix