Hi sunlover,
They are both available in either 100% natural or in a 30/70 blend (NR/SBR) and in practical terms I would treat them as being comparable in terms of durability. There are some manufacturers I know who are leaning towards Radium because the quality control seems to be a little better and more consistent on a batch by batch basis and LI seems to have had the occasional batch that has some softening or durability issues more than Radium although they have said they have recently taken some strong steps to correct this.
The firmness of each would depend on whether you were comparing the same ILD’s
LI blended Talalay comes in target ILD’s of 14, 19, 24, 28, 32, 36, 40, & 44. You can see the approximate density of each of these in post #2 here.
Radium blended Talalay comes in target ILD’s (rounded to the closest whole number) of 11, 15, 19, 22, 25, 29, 34, & 40
Latex international uses a filler in their latex formula while Radium doesn’t
Latex International 100% natural Talalay comes in N1 (14 - 19), N2 (20 - 24), N3 (25 - 29), N4 (30 - 34), & N5 (35 - 42) with nominal midpoints of about 17, 22, 27, 32, 38.
Radium 100% natural has ILD targets (rounded to the closest whole number) of 9, 13, 18, 23, 28, 33, 39, and 44
You can see a chart for Radium’sILDrangehere.
Most of the manufacturers that I’ve talked that work extensively with both say that they have a comparable “feel” although of course this is subjective. The difference between them would be relatively small and would probably reflect the different ILD’s, amount of filler, and any other differences in compounding formulas and pincore patterns they have.
Phoenix