I would suggest that unless the Tartan Thistle had invested in a bolt of Washington State tartan from Lochcarron, which they hold in stock to take kilt orders from, then the tartan they would use for your casual kilt would also be woven by Dalgliesh. Lochcarron is not going to do a short run of the tartan cloth just for your kilt.

So the differences between the two options you are considering may not be as great as you think.