Query regarding articleship

                Hi friends i got 18th rank in ipcc nov 12 exams and i have applied for articleship in all big 4s but i have no any reference.i have appeared for an interview in e&y last friday,they have selected me and they have totally internal audit work.i want to ask is it better to go for big 4 or else go in mid size firms and if internal audit has good scope in future?please guys help me i m new in the practical field.thanks