Hi Deenster,
I’ll add a bit to Beloit’s comments here (thanks Beloit Mattress Guy!).
There is more about the different types of innersprings in this article, in post #10 here and in post #16 here. I would pay the most attention to your own careful and objective testing which will tell you how the innerspring performs in combination with the other layers and materials in a mattress (versus using a latex core) and to the quality of the materials above the innerspring which is normally the weakest link in a mattress. You certainly can find a comfortable combination using springs or latex.
Post #28 has quite a bit of detail between using innerspring versus latex for a support core. Both will be very durable choices and in general wouldn’t be the weak link within a mattress, and the choice to use one over the other would be made as part of your own personal value equation.
You’re correct that the “old springs” that most of us were familiar with were the old Bonnell springs, and over time the cotton in those old mattresses would pack down into the center of those springs and then the springs would make their way through the top fabric, and they were not very comfortable. The newer Marshall (pocketed) springs do conform much more to your body than these old spring units, and mattresses like the EOS line from Naturepedic can be had with no foams on the inside – just springs. Whether or not you would find this comfortable would be from a result of your own personal testing, but there’s more of these pocketed spring units being offered in the Simplified Choice and Component-style mattress category, as these spring units are now easier to compress and ship with the new spring-reinforced edge stem that is replacing the polyfoam encasement for edge support.
Hopefully that information is helpful to you. If you have more specific questions, I’ll be happy to do my best to answer them
Phoenix