1/4" seam is fine for borders. The only time I go to 1/2" is if I have to piece backing fabrics.
Are you aware of the need to measure through the middle of the quilt, cut borders to that length, then pin borders to edge before sewing? If you just sew a length of border onto the quilt, you have a good chance of sewing excess border fabric to the edge which results in a wavy quilt edge.