I grew on barbell big lifts. Squats, Deadlifts, and bench were all ever knew. I got a kettlebell on whim just to have something indoors for days I couldn’t get to the Calisthenics park. Been swinging around this 50 LB / 22 KG orb of steel and I’m feeling and seeing a lot of improvements. Swings, presses, cleans and other mobility training has been a lot more fun and interesting. Going forward I’m gonna be rocking this thing along with my calisthenics. “Functional training” is now my goal now that i’m in my 30s. I want to be able move and groove with ease for the rest of my days, and I think this kettlebell may be the key to that goal.
You say you’ve spent time doing classic lifts, you should know yourself and your capabilities, I’d say if you know you’re strong, go for 32kg with an eye to get into the 40s - if you have any doubt whatsoever about what strong means and if you qualify start at 16kg. No shame, I started at 16kg and some of the exercises were easy and I soon went to a 24kg and then onto 32kg but some of them were a real challenge to get good safe smooth form with 16kg.