Hi Warrenjadams,
As Matt mentioned … the two mattresses you are trying to compare aren’t really comparable and are very different “animals”.
The Pranasleep mattresses would be more comparable to other Talalay latex mattresses or latex hybrids (depending on which model you are considering). I would also share Matt’s caution about the thickness of the polyfoam in the quilting layers (see post #3 here and post #2 here).
As far as the VI Spring you can see some of my thoughts about them in post #2 here.
Phoenix