This is not an exercise in hair-splitting. About the first hour or so of class on the nights of case discussions will be devoted to a group presentation of the group's solution to the case. In general, I expect each member of the group to contribute to the presentation, but the format is at your discretion. You should explain your solution and reasoning in sufficient detail to make it clear to the rest of the class. If your presentation is less than about 40 minutes long, you are probably going too fast or skimming over details that warrant further discussion.
Flashy props are fun, but clarity is the overriding concern.
The presenting group is also responsible for moderating most of the discussion following the presentation. You need not feel compelled to defend every aspect of your analysis at this point, although hopefully you will have done an analysis which you think is generally appropriate and defensible. It is probably best to entertain clarifying questions during the presentation, but criticisms and presentation of alternative approaches should be deferred until after the formal presentation. You should question anything which is unclear about the presentation and take issue with any conclusions with which you disagree. It is therefore important that you leave each case discussion with a clear understanding of how to do the case, even if you have not worked through the case in detail yourself.