AB Remote IO, Device Net and VFD's


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We've got an application in house that involves (9) remote pumping stations set along a line approx 2800ft from the main control panel. In each remote vault there is a block of AB remote IO with some mixed analog and discrete points(the flow, Pressure and level transmitters are mounted in these vaults). This goes back to the control building PLC which is a AB Control Logix system with a DHRIO scanner and a DeviceNet scanner. Each of the remote pumps are driven by an AB PowerFlex70 drive located in the main control panel ands tied to the PLC via DeviceNet. Here's the question,would it be better to let the drives handle the closed loop control using the integral PI control in the drive,with the flow meter feedback coming in to the PLC on Remote IO, and setpoint, drive control and flow feedback being fed to the drives on DeviceNet. Or,would it be better to do all 9 loops in the PLC and just pass each drive a hard wired analog output signal.We are using RIO in place of all the shielded cable runs necessary. I felt that setting up the configuration on all the drives the same,and assuming virtually the same tuning parameters to maintain the desired flow rate on each system, would result in less burden on the processor and less programming. The problem that I see would be scan time, The factory has said this application should be OK and that we should be able to detune the drives to accomplish this.
I would appreciate any thoughts on this matter