In my opinion I think the Predator and Blue Diamond were very much in the same class. It is funny having an eight sided cube of chalk. I did notice that the Predator did not last as long and I can get the chalk down the the paper or just about that. I have a piece of blue diamond that at the end of its life was 3/16" tall.
I did go back to my Blue Diamond, but I would buy and use the Predator chalk, even if its a pain to fit into my chalker box.
I just prefer the Blue Diamond. I can say they're my favorite but it also depends on the person. They would not make so many brands if people didnt rely upon them and use them frequently.
Try a cube/or octagon out and see if it fits your game.
as nice as Kamui is its still 30$ and out of a lot of players budget for recreational/league play.
Hope this kind of helps.
Predator lasted about 2 months. Blue Diamond gets me closer to 3 months, and I play almost every day.