I got a piece of the 1.21 long ago to test out and report back to John.
It feels more like regular chalk than the 0.98 when you apply it. All the other traits of the 0.98 are present except it aint as creamy. IMO on my tip it dont stick as good as the 0.98 and seems to leave more marks on the table(which I like-I like to mess up the cloth with talc and chalk, seriously). I perfer the 0.98 to the 1.21 and I have used them both lots. I havent played much in the past 5 months but was playing lots when I got the 1.21 and have used it
they are both similar and I use both, its the best chalk ever and worth the $$$. the difference isnt that big.