I've had two therapists over the years, both were great!!
I find that meetings and the ACA steps help me understand the "big picture." Talking with other ACA's relieved me of the fear of being "unique", that I was somehow flawed or "broken" as a person. ACA showed me that what I have is just a form of PTSD, no different than any other person who was raised in chaos.
Therapy gave me specific actions and exercises with which to repair my injured self. I used to be painfully shy, ACA showed me that my shyness was just absence of experience in social settings. Therapy showed me _how_ to develop social skills, one little bit at a time.
My personal experience is that I would have healed with either ACA or therapy, doing _both_ made the healing much, much faster.
Mike