I have the same concern as you. I have also asked around. The answer I get is that, Big 4 to hire ACCA grad. I have friend that manage to get into Big 4 when he only attempted < 50% of the paper. However, the case is slightly different. He used his engineering background to get in as a IT Auditor. Basically he do not do FS audit. Mostly on system audit. After a year, he request to be transferred and he got it. I might take this path as well if I can't get in with ACCA.
My friend feedback is Big 4 do hire. Chances are better if you have completed all the 14paper.
As for preference, I believe student from NTU and NUS will have a better chance but finally, it is how you perform during the interview. I think number of ACCA grad is only at most.... 1000 per year? Grad from NTU and NUS is like maybe 5 or 6 thousand? So you will properly hear most of grad from those uni getting into the Big 4 but it does not mean you do not stand a chance.
If you have a coy in mind and are unable to get, settle for a lower position and proof yourself in the coy then from there move up the corporate ladder.