As a form of exercise, it provides different benefits from walking. The movements are slower. You are in a crouched position for much of the time. This sustained posture and movement requires a longer duration of muscle contraction than walking.

Tai Chi requires a different degree of muscle and postural control compared with other forms of exercise. Keeping an upright posture while holding the center of gravity down low is required while moving from one posture to another. These are all challenges to older adults who tend to walk slowly with a short stride length and wide base of support.

No one would suggest you trade one form of exercise for another. If possible, do both. Or alternate between the two. In this way, you'll gain the benefit of both kinds of exercise. Exercise of all types is important since falls and fractures are the number one cause of death and disability among older adults.