Alloy Composition workability

In india the goldsmiths normally call the following mixture as
"white metal" (not white gold)l:

Gold 25%
Silver 75%

Can some one assist me if the following composition with addition of
little bit of copper would be a better option in terms of
workability, tarnishing, color, oxidation etc(Chemical properties)
compared to the above.

Gold:18.5%
Copper: 7.5%
Silver: 74%

Regards
Rahul
India