For bed quilts, the size should take into account the size of the bed, the depth of the mattress, whether there is a footboard, whether the user wants a pillow tuck... For king or queen, this usually means a quilt that is close to square, or even wider than it is long. For a twin or bunk bed, rectangular is better. A full bed could go either way. For a throw that I snuggle with on the couch, I prefer square. So... I guess my preference is with a square quilt. Most quilt designs work out better with a square too.