Hi tsunamis,
The single biggest factor in the quality/durability of a memory foam material is density (see post #4 here for more about durability) but there are many differences between the properties of different types of memory foam made by different manufacturers that can affect how a particular version of memory foam feels and performs (see post #9 here and post #8 here).
“Eco friendly” memory foam would be more about marketing than reality. There is more about eco friendly or green materials in post #4 here.
There is more about the different ways to choose a mattress (locally or online) that can help you assess and minimize the risks involved with each of them in post #2 here and there is more about the most important parts of the “value” of a mattress purchase in post #13 here that can help you make more meaningful comparisons between mattresses.
Phoenix