Whatever is 100% cotton is the only thing to use for patch material.
With all due respect Swampy, but linen was more widely used in the 18th and early 19th Century than was cotton, so linen can be used successfully, but...
Good patch material is more determined by how tightly woven the material is and not so much what it's made of - as long as it's a natural fabric that is - tightly woven hemp works good too.
That tight weave is why pillow ticking is so widely used - plus it's relatively inexpensive, which linen is generally not.
So for quality (and price even though you said that didn't matter - my Scots blood talking :grin: ): pillow ticking, cotton canvas, cotton duck, denim, etc. works as good as you're going to get, so IMO there is no sense in using linen unless you want to be as "PC" as possible.
I have used linen (scraps from clothing projects), but my main go to patching is pillow ticking or cotton duck.
What's best? along with the ball size, lube, and load it all depends - try several combos and use whatever your gun likes best..
The above is based on 45+ years of shooting smoke poles and experimenting with all kinds of load combos......I never found linen or hemp to be any better than a cotton fabric os some type....
Of course then there's silk..:hmm: :thumbsup: :hmm: