First, silver is the best electrical conductor. Copper is 2nd in line. Silver conducts 7% better than copper.
Teflon Jacketing.. Teflon is inert. Some other materials are not.. teflon is used during surgery for this reason as it won't react chemically and wreak havoc.
Teflon has been proven to be the best insulator for wire. Thats why the military uses it. That's why RF cables use it. Other materials counteract electron flow, especially so at high freq. ranges.
Mr. Jim Willams(the modification wiz) uses teflon coated silver wire in his projects. has been for years.
He (and others) have said that it sounds better than Kimber PBJ stock (teflon/copper) , which is much more usd per foot.
When in doubt, find out what the pros with years of experience use.Then find out why.
Thats what I do. Havent been dissapointed yet with advice ive gotten this way.