10.5.5         When to use PolyLine vs. Line

Each Segment of the Curve Line will become a separate object. These can be deleted and edited separately.  The shape drawn with Line will contain many objects.  Scaling or moving the shape may result in gaps between end points that will “leak” if you fill the shape.

Use Polyline if you want to draw a single object with segments. Polylines do not “leak” when you fill them.  Curve and Straight lines can not be mixed in the same Polyline.  But, Arc and Straight lines can be mixed in the same PolyLine.