So it depends on your physiology, but a lot of people develop asymmetrically (carrying kids on one side, etc) or have a skeletal issue like scoliosis that causes that. Lifting - and by lifting I mean the big important movements like squats, deadlifts, OHP and benchpresses - works both sides of your body at the same time. Yoga breaks it up into one side at a time, which I've found has caused my body to become a lot more symmetrical. Yoga also includes a lot of strength movements that also improve flexibility, which lifting does not.

Hard to get into a debate about this because lifting does an amazing job of exercising just about everything. It just does it in a very different way with, I've found, higher risk of injury.