I'm in Situation 2 and I'll certainly try to include some miniature research/discussion groups but the issue I have with waiting until the assessment is that I always feel some of the students are both not understanding a concept and not asking questions about the things they don't understand. That is why I like the process of questions/answers and having students summarize processes because it provides a way to check their understanding during class so I can redistribute time spent on a subject on the fly. I've already passed up the time at which the information would be fresh and in-context if I review it after the test/quiz.