It seems that quite a few schools perfer the GRE to the GMAT for a business PhD. For example, Wharton will only accept a GRE (unless I'm reading it wrong):
Either the Graduate Management Admissions Test (GMAT) or the Graduate Record Examination (GRE) may be taken for admission to most programs. For Business and Public Policy, Ethics and Legal Studies, Real Estate, and Statistics programs, only the GRE is acceptable. All applicants must provide tests scores; applications without GRE or GMAT scores will not be considered.
Should I plan to take the GMAT or GRE? I'd hate to waste my time studying for the GMAT only to find the school wants the GRE. Can someone please clarify which test is more accepted for a business Phd? Or is there any advantage to taking one over the other?