Hi AcGolfer,
Post #2 here has some of my thoughts about the differences between a latex hybrid and an all latex mattress.
2.35 lb polyfoam is a high quality material and because the upper layers are the most subject to wear and softening … the durability difference between them would not be a major factor … especially with your lower weight. The main difference between the two would be in feel and performance. Latex would be more conforming and adaptable as a support core layer and for most people would be closer to a waterbed in feel and performance than polyfoam (which is “stiffer” and less “point elastic”).
Because the upper layers contribute more to how a mattress feels for most (but not all) people than the deeper layers … a latex polyfoam hybrid with good quality polyfoam in the support layers is a good budget compromise. In your case I think that performance and feel would be the biggest difference between them and durability would be a secondary and lesser factor.
Phoenix