Hi chrisw,
I’m glad you were able to replace your defective mattress … that’s good to see (the replacement that is not the defect) :).
Primary support comes from the deeper layers of a mattress not from the top layers and it’s difficult to “fix” a mattress that is too soft by adding layers on top of it. The comments and replies in this topic from yesterday which was about the same issue (a memory foam mattress that is too soft) would apply to your question as well.
This would be a preference choice rather than a better/worse choice. There is more in post #7 here about the differences in “feel” between Dunlop and Talalay but the best way to know which one you prefer would be based on your own personal testing and/or experience.
Phoenix