A recent study published in The Journal Of Sports Medicine And Physical Fitness compared the back squat and the leg press, not only for strength development and body composition improvement, but also for several functional measures as well. Scientists examined three groups of subjects. The first group performed the squat twice a week for 10 weeks, while another group did the leg press, and a third group did both exercises.
While most people tend to think of the squat as the superior exercise, the results were quite equitable. The group who squatted did see more relative strength gains. However, improvements in body composition, while modest, were nearly equal across all subjects. Both groups improved functional metrics, such as balance and vertical jump.
Overall, the combination group performed slightly better on the functional attributes. This is just another reason to include both barbell and machine exercises in your workout.