For trauma I believe a psychologist is best, just because trauma therapy is based on the scientific understanding of how trauma affects the brain and has quite specific, research based interventions. It isn't just "talk" therapy or about the relationship. It's about learning to recognize the neurobiological responses of the brain to triggers and how to respond to those triggers to create different outcomes.

But this might be different in my country than it is to the US. "Therapists" here only have to have a counselling diploma, which may or not be equal to a bachelors degree.