Project Curve and Imprint Curve may look similar, but they are used differently.
Imprint Curve takes that curve and makes it part of the body’s topology, giving you selectable edges that can be used for cuts, trims, offsets, bevels, and more.
Project Curve lets you place a curve onto a surface so it follows the form of the model.
Project when you need surface following guide geometry.
Imprint when you need editable body geometry.