When the path and guide curve have different lengths, the sweep will have the length of the:

In the context of a sweep feature in SolidWorks, when a path curve and a guide curve of different lengths are utilized, the resulting sweep is influenced primarily by the length of the guide curve. The sweep feature essentially follows the path while being constrained and directed by the guide curve.

Since the guide curve dictates the orientation and shape of the profile along the sweep, its length becomes the defining factor for how the final geometry of the sweep is established. Thus, the sweep will be constrained to the length of the shortest entity, which is the guide curve in this scenario.

This means that regardless of the longer path curve, the sweep will only extend as far as the guide curve allows, effectively making the final geometry's length equal to that of the guide curve. Thus, when considering different lengths of the path and guide curves at a sweep, the outcome aligns with the length of the shortest entity, leading to this choice being the accurate one.