My main suggestion is not to overcomplicate it - these sorts of presentations are best kept straightforward and simple, with plenty of signposting and a clear, easy to follow line of argument with some nuance in analysis. Bear in mind time constraints, practise speaking to time and build in time for interruptions if necessary, research well but equally don't drown yourself in data.
Remember that, even though you have to come to a conclusion, you should avoid being enormously political here - easy for me to say that, it's one of the debates I'm absolutely the most passionate about - but you need to bear in mind your assessors may fall on either side of the debate and, frankly, you don't want to give someone an excuse not to assess you in a good light.
Finally, remember to relate key points back to the firm - it's easy to get caught up in the politics and arguments, but if you forget the law firm part you're making yourself fight a massively uphill battle.