I piece my borders. When I quilt mine I usually do an all over meandering so the seam from the border piecing doesn't even show. Iknow that is what alot of people think when you speak of when that is mentioned. Now if I was going to do a design on my border, then I might consider a straight piece.
Usually I make my quilts and then know what size border I am putting on it so cutting the border out first from a long strip doesn't help me because I don't know what will look nice when it is done.
Barb