Hi there,
thanks for asking your question on our Consulting Q&A! It's a good question :)
You could say that the purpose of a Case Study is to simulate your case interview situation, whereas the purpose of the Project Simulations on PrepLounge is to similate your real consulting job.
This means that the Project Simulations go a step further than the Cases. They simulate a project you would work on as a real consultant, starting with the project brief and ending with the PowerPoint presentation for your client.
For your case interview preparation, your focus should definitely be on practicing cases with case partners (or experts). Your main goal (at first) is to ace the case interview! Once you have reached a very good level, you can go through Project Simulations as a bonus in order to get a deeper insight of the consulting job.
You have free access to a Project Simulation, so feel free to check it out!
Hope this helps!
Astrid
PrepLounge Community Management