I came across Miller & Duncan in an audio by Rick & Sherry Stolp. (My post & links here)
This research makes more sense than most, as it is strongly practice based. The difference between modalities is not as relevant as the therapist, for example. Listening to your clients feedback is important and responding accordingly helps!
Barry Duncan on YouTube
The Good, the Bad, and the Ugly of Psychotherapy: Practice Based Evidence to the Rescue