A separate double-fold binding will wear longer.
And if you bring the back around it may not be a match for the front fabric.
And the opportunity for a final 'statement' with your binding is gone.
And last, quilting shrinks the body of the quilt, and by folding the backing fabric around for binding, the edges end up wavy.
Yet I sometimes will use that method on charity quilts as it is so much faster IF: the fabric is a good complement for the front, the batting is flat, and the quilting isn't heavy.