Hi librarygal,
There is more about the different types of latex and how they feel and perform in this article and also in post #2 here and post #6 here (which talks more about “organic” latex and the benefits and “value” of different types and blends).
In an apples to apples comparison … most people wouldn’t feel much difference if at all with only a 3" layer of blended Talalay vs the same ID and thickness layer of 100% natural Talalay although they may feel more differences between two mattresses where the whole mattress was made of one or the other type of Talalay.
There are some slight differences in the manufacturing of the European Talalay (Radium) and the American Talalay (Latex International) but in practical terms they would both make good choices and I would be perfectly comfortable with either one and would use the one that the mattress manufacturer felt was the better choice unless you had a particularly compelling reason to make a different choice.
Bear in mind too that both types of Talalay (100% natural and blended) may not have the exact same ILD’s available and that the two main Talalay manufacturers may also be slightly different in the exact ILD’s that they offer.
The differences belong to the process and the material itself rather than the manufacturer because they would be inherent to the properties of synthetic latex (SBR) and natural latex (NR) itself rather than unique to each manufacturer or the country of origin.
Hope this helps
Phoenix