Siemes PCS7 to AB SLC's

Looking for opinions on how best to interface a Siemens PCS7 controller to Allen Bradley PLC's. Micrologix & SLC500's.

I see where they have echo change Ethernet/IP gateway.

I also see that Profibus is another option.

Looking for other oprions and what are the pro's & cons of one versus the other.

As always your help is greatly appreciated.

How much data you need to exchange?

I really don't know at this time. I would assume it to be small as the AB PLCs are doing all controll now, eventually the plan is to replace the AB's with PCS7.

Have you some plan on stages on replacing control with pcs7? Do you plan to use ab as just io at one point, or do you have possibility of just shutdown for duration of overhaul? If there is possibility of large amount of data to be transferred at one point, i see no reason to use anything other than ethernet based system.