PWC or Private!?!?!

Hi guys I have an interview with Pwc for a client services administrator role and I have a couple of questions which I hope someone may be able to help me with, I will try to keep this short.

I aim to become a Chartered Accountant and have 4 exams left of my ACCA qualification.

I have secured a role as a finance assistant within a large private firm and I am due to start soon.
I also have an interview with PWC as a client services administrator and am somewhat stuck as to what path to take.

If I was successful in my interview with PWC what kind of progression can I expect from this role?

Should I go with PWC or pursue my role with the private firm and apply at one of the big 4 later down my career?

I hope you can help me.