The Fijian-born duo have reputations as world-class try-finishers, but Smith has praised their defensive work ahead of the second test against France in Paris later today.
"Both wingers have improved their defensive work immensely," Smith told website stuff.co.nz.
"If there are any better defensive wingers in the world than Sitiveni Sivivatu you better give them a New Zealand passport and send them over.
"He takes the high ball well, he covers the ball in behind him and covers well on the other side of the field.
"And Joe's chasing work-rate is exceptional, he's a big tackler and he shut down some dangerous moves in Lyon."
Smith says the softly-spoken pair's increased communication with full-back Leon MacDonald had assisted their progress.
"We asked them to improve their talking and the word from Leon MacDonald is that the talking was as good as any he's had from the wings," said Smith.
" When the ball's in the air he needs talk from his wingers and he's getting that."