During residency Primary care education will be mostly oriented on outpatient clinics etc. compared to categoricals PC track does 2 months more of Ambulatory Care Rotation ( Categoricals do elective or wards during that time).
Usually ppl from primary care go to General Outpatient practice
Categoricals to general in patient practice.
Both tracks have same chances in regards of Fellowship. meaning that if you are PC resident and decide to do ID - you can go for it
THIS IS MY PERSONAL OPINION: Programs get more slots for residencies if they have 2 different tracks ( Cat. and PC ), compare that to program that has only Categorical.