Hi James,
As such there is no tool or report available to compare ECC and APO master data.
You need to download the data from table of location product etc from APO and ECC side and then do the V lookup. You can also call report RIMODSRH using transaction CFM5. The system displays a list of all filter objects that correspond to your selection criteria. You can use the Details pushbutton to navigate to the list of material/plant combinations for the filter object type selected. You can use the Models pushbutton to display the integration model in which the selected material/plant combination already exists, and to see which activity mode is valid.
Regards,
R.Brahmankar