Let me throw a couple of pennies worth into this.

Machine stitching does not have to show a stitch line. There are many ways to hide the stitches by selecting the construction method.

Some hand stitching can be downright unsightly.

It is not always the method of stitching that determines quality and/or longevity. It is stitch tension. Consistant tension produces flat, even seams. It evens out stresses. A line of uneven stitches leaves a puckered seam that overstresses the tight stitches causing failure.

The reason that machine stitching seems (stress seems)to last longer is that the machine is controling thread tension. Few people today have the talent or patience to hand sew with machine quality even tension.

If you are evaluating the quality and potential longevity of a new kilt, look at the seams. Pull on the seam slightly. If it opens up to reveal the stitching, with some stitches loose and some stitches tight, pass by and look for another kilt. If, when you pull, do you see small puckers form around some of the stitches and lay flat around others, this seam will fail.

Look at the seam lines. Are they straight where they should be straight and do they form fair curves where they are supposed to curve? If you stress the seam, does it keep the same shape under stress as when relaxed? If it changes, pass it by.

To people who sew, and take pride in their work, it is the seams that matter. It is those thousands of individual stitches that we look closely at.

I can always tell when a person who sews picks up one of my kilts. They don't hold it up at arms length and comment on the fabric, they put on their glasses and look closely at my seams.