Hello,
I totally agree with Luke. In addition, let me mention that any good SAP HR expert should feel home pretty quick with Employee Central from a pure business process perspective. Payroll is payroll, time off is time off, even if the processes can evolve overtime.
To start off your project moving things from SAP HR core to SuccessFactors Employee Central, make sure you have the right skills at hand. If you do not have the rare pearl that brings both SAP and SF expertise, I’d strongly recommend a tandem SAP&SF. But such pearls are becoming less rare those times, many partners can provide you with such dual profiles.
Best regards, Yannick