I agree with everyone else that a pieced back gives you the opportunity to jazz up the back if you add some of the colors from the front to the back. I recently did that with a quilt- added a 10 horizontal strip that started out about a foot from the top. When the quilt is laid on the bed and the corner is turned down you can see the pretty strip on the back. It really enhanced the look of the quilt.
However- I also just learned about diagonal piecing the back. That also might be on option if you have extra length.