What is the "best" division to work for in a Big 4 company?

Which ever you enjoy most.

And how are you meant to know this when you're still at uni....

Research different departments. Attend the sessions to meet the people who work in those departments. You don't want to be in a job you hate for 3 years, and as much as people think Accounting is all the same there are huge rivalries and different departments really do suit different people.

I agree people need to research more but really unless you do an internship you're not going to know what their jobs are like day in-day out. Finding a department with a good group of colleagues is probably going to be the best thing you can do if you want to enjoy your job. But really how are you going to find out about all the people in all the firms?

But surely with a bit of research of what the departments do (and asking people that work for them at events you'll find they're very open) will give you a good idea of what sounds more enjoyable to you?

That must be so much more meaningful than any fractional extra prestige you might think you have from being in a certain department and to be honest day to day I don't have any thought about the prestige of one department over another while I'm at work. The closest I can see is that you might get some prestige from having certain clients, especially when you get to assistant manager and above.

In reality I think most people get their sense of prestige from the firm they work for, not the department.

Some divisions are harder to get into and pay more. This is why there is probably prestige associated to them. Each firm will also be better at certain things or in certain sectors so it may help to try to place yourself with a particular division/sector.