Hi cpaciente,
I don’t have any personal experience with either topper but I can make a few comments.
Based on the description on Amazon and on their site here … there seems to be some conflicting information in the description that would lead me to question its accuracy.
The descriptions say that there are no seams and no adhesive which means that it wouldn’t be Talalay latex because both Radium and Latex International use glue seams in their king size layers.
It also says “made in USA” and “no fillers” and the only Talalay that is made in the US is latex International which uses fillers in their Talalay.
The wording … “No seams - No fillers - No Adhesive” is usually an indication of a product that comes from Latexco and if this is the case then this topper is most likely their Puralux product (which is made in the USA) which is typically a 20% natural and 80% synthetic continuous pour Dunlop blend (although they can make it in other blends as well). If could also be their 100% natural Puralux product but this would be made by a different manufacturer which they supply (typically Latex Green) and isn’t made in the US.
Of course this is all speculation but I would be cautious and I would always confirm the type and blend of any latex topper you are considering to your satisfaction.
I don’t have any personal experience with either topper but I have no reason to doubt the Malouf website which says that the Isolus is Dunlop (although they don’t mention whether it’s 100% natural or a blend).
Post #2 here and the topper guidelines it links to have more information that can help you use your actual sleeping experience to choose the type, thickness, and firmness of a topper that would have the best chance of success and also includes a link to a list of the better online sources for toppers that I’m aware of as well that all provide reliable descriptions for their toppers.
Phoenix