I can't see a noticable difference in the swing or warmth of my various weight wool kilts from various mills. I would recommend going with the color you prefer - be sure you see a real swatch first.

A personal preference is to have tartans that are important to me done up in the top of the line material - but I also have taken light weight cloth to get a kilt made in a tartan I like.

Bottom line - "Sorry cousin - there isn't an easy answer....pick one and enjoy it."