Sterling silver is so much easier to buy in Canada but I'd rather pay about 50 cents a foot extra and pay extra shipping to get Argentium from the U.S. for several reasons. The only alternative in my mind is fine silver (.999) and I do buy some, but it doesn't work harden enough for some purposes.
Sterling silver is 92.5% silver and 7.5% alloy, usually copper.
Argentium silver is 92.5% silver and 7.5% germanium alloy. Germanium is used mainly in fibre-optics.
Sterling: Tarnishes easily
Argentium: Very tarnish resistant. It will tarnish but very slowly and more a golden color than the black of sterling. To me, it's a real selling point, because people worry about silver tarnishing.
Sterling: Can turn color on some people and others cannot wear it because of the copper alloy.
Argentium: So far, I haven't heard of anyone with a germanium sensitivity. It should open up the wearing of silver to people who previously couldn't because they reacted to the copper alloy.
Sterling: Must be soldered.
Argentium: Can be fused to itself.
Sterling: Must be completely heated in order to solder.
Argentium: Only needs the small area around the join heated in order to solder or fuse.
Sterling: Is prone to firescale because the copper alloy rises to the surface when heated. Too much fire for too long will cause a firescale that can't be removed because it reaches below the surface.
Argentium: Is not prone to firescale. Heating a smaller area uses less fire for less time for starters. And the germanium does not cause firescale like copper does. Argentium can be pickled but any discoloration from torch work usually just wipes off.
So those are my reasons for sticking to argentium. So far, I've found that Rio Grande and Monsterslayer are very close price-wise and are the most economical suppliers, not to mention the fact that they have a wonderful selection now. I still have a spool of sterling in my drawer but it will probably be going in as scrap to help pay for my next shipment of argentium. That's how much I appreciate the difference in the two silvers.