In a word, yes. They have the biggest clients, fees etc. Your question is just like asking are non-MBB strategy firms just the same as MBB, or are non-league sides better than the premiership. Of course the actual ACA itself is the same, but the quality and breadth of client work isn't at all, as well as additional non-ACA training, including the calibre of managers etc. who you learn from. Yes, there is the prestige factor - but this is simply a relfection of what I said above. Also, it is harder to work for big4 and so people from there are usually filtered out from the rest to start with. In short, go for the big4. Many/ all of the best jobs stipulate for ACA qualified from these firms.