No two repairs need quite the same treatment. It is important to choose the most appropriate method for each job. The question is not simply shall I darn or shall I patch? There may be a better way to suit the shape and cut of the garment, and the position and size of the area should be considered carefully before you start any repair and this should influence the chosen method.
This is a matter of ingenuity and fashion sense as it may be possible to cover the area in the same way that will not suggest any repair or alteration but instead will appear to be part of the styling. The area could be covered by a trim, such as braid, ribbon or lace. The possibilities are endless and their suitability should depend on your own taste.
Should you have enough matching fabric, it is far better to replace a whole panel of a garment than just to patch it.
This is the simplest and strongest way to repair a split seam. A split seam may not be easily accessible from the wrong side either because it is in a position where another seam crosses it such as an armhole or because the garment is lined.
A fallen hem should be re-stitched in the same way as it was originally made. Thin fabrics are usually turned in and slip hemmed