Hi SuperJ,
I would avoid coil counting as a way to determine the quality, durability, or value of a mattress because an innerspring isn’t normally the weak link in a mattress and the number of coils is only one of many factors that determines how a particular innerspring will feel and perform inside a specific mattress design and can be more misleading than helpful. There is more about the different types of innersprings in this article and in post #10 here.
While “in theory” a latex support core may be more durable than an innerspring … the support layers of a mattress are not usually the weak link of a mattress (a mattress tends to soften and break down from the top down) so in practical terms a latex core and an innerspring support core would both be durable choices and the materials above the support core would be a more important factor in the durability and useful life of a mattress.
There is more about the many variables that can affect the durability and useful life of a mattress in post #4 here.
I would pay much more attention to your own careful and objective testing which will tell you how the innerspring performs in combination with the other materials and components in a mattress and to the quality of the materials above the innerspring (which is normally the weakest link in a mattress) than I would to the number of coils in a mattress which by itself isn’t particularly meaningful.
Phoenix