Why use Spartans when you have Tactical Dolls?

The Spartans hated them, they were A.I. but competing with the Spartans. The ODST that knew about them were terrified of them, and even ONI did not really feel comfortable with them. Tactical Dolls were not normal A.I. as far as the UNSC understood it, certainly their programming had removed rampancy from UNSC A.I. but these A.I. had bodies. (Prologue has been totally rewritten)