Nick,

Chapuis have a reputation for being very accurate/well-regulated. So the two barrels shoot the specified regulation load (i.e. Norma 286grain Oryx 9.3x74 load) to the same point of impact at the regulation distance (often 50 metres).

Sabatti sold a bunch of double rifles through Cabelas. Apparently they adjusted regulation by cutting the barrel crowns at an angle instead of re-soldering the barrels at a different angle. It didn't look good, though apparently it did work pretty well. But it's not the correct way to do this, and there are scores of people ranting across the internet about it. Cabelas tried to "fix" this and let people return the guns. Sabatti re-crowned some and re-regulated I guess. People who have the Sabatti's though seem to think they're pretty good guns.

Never heard of Gaucher either.

JP Sauer made solid guns. Probably so did Wilkinson. Current state of those guns would be unknown, though, and expensive to feed per earlier responses.

Hope this helps,
Steve