The main difference between a 12-passenger Ford Transit van and a 15-passenger Ford Transit van lies in seating capacity, interior space, and size. Here are the key distinctions:

1. Seating Capacity:
- The 12-passenger Transit van has seating for up to 12 people, including the driver, with 4 rows of seats.
- The 15-passenger Transit van has seating for up to 15 people, including the driver, with 5 rows of seats. It offers additional seating in the rear compared to the 12-passenger model.

2. Interior Space:
- The 12-passenger van offers more cargo space behind the last row of seats compared to the 15-passenger model, as it has one less row of seats.
- The 15-passenger van offers less rear cargo space due to the extra row of seats but can carry more passengers comfortably.

3. Size and Length:
- The 15-passenger van is generally longer than the 12-passenger model, making it slightly more challenging to maneuver in tight spaces.
- Both models may be available in standard or extended lengths, but the 15-passenger van tends to require more parking space.

4. Weight and Performance:
- The 15-passenger van may be slightly heavier due to its additional seating, which can impact fuel efficiency compared to the 12-passenger model.

In summary, the 12-passenger Ford Transit is ideal for groups needing more cargo space and easier maneuverability, while the 15-passenger Ford Transit is better suited for larger groups requiring more seating capacity.