If you are a target shooter, needing the utmost in accuracy to even have a chance to place in a shooting match, then use the Swiss powder. Other than that, the difference between the two powders does not justify the extra cost for the Swiss powders.
My brother and I spent some time a year ago trying to resolve this very question with his .40 caliber Chunk Gun Rifle. We found that if we screened the Goex 3Fg powder, to remove the fines, as well as screening the Swiss powder to keep the two even for the test, that the difference in velocity was reduced. When he used an OP wad with both powder charges, the velocity difference closed much more, and there was NO apparent difference in the kind or amount of powder residue in his barrel. Finally, he found that he could add a few more grains of Goex FFFg to his load and equal the velocity he was getting from the Swiss powder.
For that reason, we decided that the 1/3 more cost of Swiss powder is just not worth the money. That does not mean that we won't continue to test and experiment with a can or two of Swiss powder, but for general shooting, and all off-hand or cross stick matches, we do just fine with Goex powder. ( or Wano, Schuetzen, Kik, Graf, etc.) The secret is to screen the powders to remove the "fines", as that seems to give the most consistent velocities( lowest SDV) with any given powder.
You can buy screening from
McMasters.com in the correct mesh sizes for this purpose.
Fg powder must not pass through a screen with 14 x 14 mesh( 14 wires per inch)
FFg powder must not pass through a screen with 24 x 24 mesh.
FFFg powder must not pass through a screen with 40 x 40 mesh.
FFFFg powder( if you actually want to bother) must not pass through a screen with 50 x 50 mesh.
I priced the 40 x 40 mesh a couple of years ago at less than $10.00( $7.33 to be exact) for a square foot of screen. If you buy one of those needle point hoops at a hobby store, or craft store, you can glue, or staple the wire screen to the hoop and make your own screen for your powders. Otherwise, you can build a frame from wood for next to nothing, and a few screws or nails.
My brother bought the Graf & Sons powder screening drum, with screen for FFg and FFFg powders. He does not shoot anything that uses Fg powder. He found the "fines" that pass through his FFFg screen make terrific flash powder for his flintlocks. Not much of it, but its great flash powder.