We first need to consider who the individual is that we are talking about. Is it a 20 year old College Football player or a 40 year old sedentary accountant? What is their injury history look like? What are the demands of their sport? How well do they move and learn new movements? Lastly, and most importantly, what are their goals?
Despite what you may think to the contrary, there are no magical properties to barbells or kettlebells. I can make your lower body damn strong doing barbell front squats or double kettlebell front squats. You may be golden with just goblet or bodyweight squats. Can’t press a bar overhead effectively? Try a single arm press with a dumbbell or kettlebell.
You may have started to notice a pattern emerging here. The training implements may change, but they don’t really matter. I can make you stronger, a better mover, and more fit with any of these objects. What matters is the movements themselves. Are you pulling, pushing, squatting, hinging, and carrying on a regular basis? Perfect. I’m not going to try and jam a round peg into a square hole by thinking that everyone must do x exercise or they will never improve. People have different needs and abilities, but as long as you are hitting each category you will make them better.