The main difference between free weights and a universal machine is that universal machines are generally safer because the weights are not positioned above the body and they provide more support and stability for the user.
Free weights allow for a greater range of motion and can engage more stabilizing muscles, but they require more balance and technique. Universal machines typically guide the movement and can be easier for beginners to use, making them a good option for safety and proper form.
The statement that "universal machines build bigger muscles because they allow for more repetitions" is misleading, as muscle growth is influenced by various factors including intensity, volume, and individual training programs, not just the type of equipment used.
Overall, while both types of equipment have their benefits, the primary distinction lies in their design and the level of stability and support they provide.