I only have one KB at the moment. It is the 16kg. It's fun. I'm amazed at how much you can work yourself with just 35lbs
I want to get another one. ($ is in tight supply with 2 4 month old babies to feed).
I was thinking of getting a 53lber but might opt for a lighter one (somewhere in the 44 lb range) sorry for the use of lbs instead of kg's. I don't want to hurt myself as I am self taught. I'll get proficient at the 44 lb kb and then move up the ladder.
I have an Ader KB. It is the only KB that I have used...It seems like a good one, but I am not an expert.