well kettlebells and dumbbells break your grip. as in they are 2 dimensional. clubbells are an extension of your arm so they are movement in 3d if that makes sense? clubbells are also way way heavier than the equivalent dumbbell. i got them to help strengthen my rotator cuff as i had stuffed it and i wanted to make it stronger so as it didnt happen again. personally i find they activate the core and the lower back with almost every exercise i do. things like barbarian squats are full body in a way barbell,dumbell or kettle bell squats arent. i reckon they are better too as they keep your balance and agility going all the time.
Ultimate Mass Builder - Clubbell Barbarian Squat - YouTube
i also do double arm casts and iron crosses.
Clubbell - Iron Cross - YouTube
this is a bit of fun too. medieval weaponry. clubbells would be awesome training for lots of these!
The Medieval Mace - YouTube