Hi Failed Engineer,
As far as I’m aware the blended Talalay from both Radium and Talalay Global (previously called Latex International) is closer to 70% synthetic and 30% natural than a 60/40 blend but either way it wouldn’t make any difference. The blended Talalay from Talalay Global would be the same product between different mattress manufacturers regardless of how they are described and the same would be true for the formulations from Radium. There is more about the different types and blends of latex in post #6 here. There is also more about some of the general differences between Talalay and Dunlop in post #7 here.
The choice between the feel and properties of different types and blends of latex would be a preference and budget choice more than a “better/worse” choice and any type or blend of latex is a very durable material relative to other types of foam.
As you probably know all of the vendors you are considering are members of this site which means that I think highly of all of them and that I believe they all compete well with the best in the industry in terms of their quality, value, service, knowledge, and transparency. You are certainly looking at some very good choices.
Once you have narrowed down your options to a list of finalists that are all choices between “good and good” (which you have) and you have confirmed that none of them have any lower quality materials or “weak links” in their design (which they don’t) and if at this point there are no clear winners between them (which is usually a good indication that you have done some good research) then you are in the fortunate position that any of them would likely be a reasonable choice and post #2 here can help you make a final choice based on any local testing you have done, your more detailed conversations with each of the online options you are considering, your personal preferences, your confidence about PPP and the suitability of each one, their prices, the options you have after a purchase to fine tune the mattress or exchange or return the mattress (or individual layers in some cases) and any costs involved, any additional extras that are part of each purchase, and on “informed best judgement” based on all the other objective, subjective, and intangible parts of your personal value equation that are most important to you.
Phoenix