Wampus, you must have sit through the same Joe Keeslar tutorials as I did. I've been using the full soft pure silver and really like it. I made my tools from screw drivers, hack saws, etc.
Chris,
I hav'nt tried anything else, because I use the flat wire. Most all of the copper scraps will be round. I guess you can roll them out flat in a rolling mill and anneal em. Rolling mills are expensive though. So you might want to spend the money on good wire.
The pure silver is expensive but goes a long way.
Lin