Strengths and Limitations of EL Instructional Models and Protocols

In comparing EL Instructional models, for example, GLAD, SIOP and even Madeline Hunter's model, there are many similarities. For instance, all begin with accessing prior knowledge and end with some sort of assessment/closure piece either included in a daily lesson plan or in a lesson plan that extends over a few days or longer. It would be interesting to get your ideas about the strengths and limitations of each model. What successes have you experienced using one or the other? And, if there is a limitation, what is it? And what piece could be added to strengthen it?