Hi Davison
1. There are Two Work centers in IW38 screen, See this picture:
2.Both Tcodes take you to the same Program screen (SAPLCRA0). , the Value of 'Work Center Cat' differ. It is 0005 for Maint. Work Center. and 0001 for the Other (PP Work Center), Often PM people do not use this field).
Jogeswara Rao K