The essential difference between the original graduate school clinical psychology training model, called the Boulder model, and the later graduate school clinical psychology training model, called the Vail model, is their different emphases in training orientation.
The Boulder model (named for a 1949 conference in Boulder, Colorado) emphasizes scientific grounding in clinical psychology. This came from early efforts to have psychology recognized as a legitimate "hard" science.
The later Vail model emphasizes a practical experience grounding in clinical psychology. This means the emphasis is akin to the emphasis in teacher training, which requires a year of student teaching practicum in order to be certified. Thus the Vail model requires that practical experience during training be acquired at a rate higher than is required in the Boulder model.