Get access to everything we publish when you sign up for Outside+.
Answer: It depends on your goals.
Research found that traditional straight-set lifting using free weights increased muscle size and strength — good if you’re looking to sculpt and shape specific body parts. But training with kettlebells was shown to increase power, endurance and strength, and because you activate dozens of muscles versus just a few, you’ll burn more fat and boost your metabolism. So if you have the space and the funds, invest in both for a well-rounded and balanced physique.