Following possibilities are provided in order to compare sources:
Comparing Source Code-Based Development Objects in the Current SAP System
Comparing Programs in a Remote System
To compare a program in the current system with one in another system, choose Compare different systems from the initial screen of the splitscreen editor. A field appears on the screen in which you can enter the RFC destination of the SAP System containing the required program.
In the RFC destination field you can only enter systems for which an entry exists in table RFCDES.
A remote comparison is not possible for methods.