Full plaids

[MacAngus]

I would say do what you want you're the one wearing it.
However I think the stitched ones look better.
I have a scottish national modern pipers plaid and it hangs fantastically and looks sharp under the cross belt.
I had one that wasn't stitched and it was kinda a pain in the butt.
It also looked sloppy.

[Twa_Corbies]

I would go with a heavier weight for the full shoulder plaid, as these were worn not only for decorative use, but so that they could serve as a weather resistant covering in cold, damp and rain; the idea being that you could use it like a blanket or drape it about you as a sort of poncho if required. I would use a good 16 oz. fabric, you will want it to be double width (54") and about 3 and a half yards long. The ends should be fringed in twisted tails like a piper's plaid, which can be cone yourself if you have the patience. The fringe tails can have either one or two colors of thread in them, but should never have more than two colors per fringe tail, so it requires a bit of math to figure out how to divide up the threads befor twisting them together.