Equine assisted psychotherapy has a strong rate of carryover into other areas of people's lives. I support it.
Equine assisted physical therapy does not demonstrate good carryover into other areas of a person's physical needs.
The problem with both is the cost. A practice that uses horses is not paid any more than a practice that uses an office and furniture or exercise equipment by instance companies. I'm lumping both psychotherapy and physical therapy together. But with equine assisted therapies there are three additional costs of horses, tack, stables, feed, veterinarian care.
A large amount of time and energy goes into fundraising when horses are used.
I suggest you study the discipline that interests you the most and seek to incorporate horses into your practice as you find opportunity.