I know first hand about Accenture Strategy, and what I can tell you is the following:
1) Forget about IT matters, ACN Strategy think about business problems (in the broad sense)
2) The interviews (at least in my case) always were a text to be evaluated afterward
3) The business case format is much more conversational than other consulting firms (interviewer-led), the Potentia test is the other way around - you talk all the time.
4) Potentia subjects are like poverty, education, guerrillas and case interviews are like MBB cases but easier (but keep in mind all the business concepts)
Hope it helps!