Best is probably a clinch or Palomar knot. I don't use either one. I've always used a double Turle to bend the fly to tippet, since it has about the same strength as the blood knot that joins the tippet to the next larger diameter leader section. The clinch and other stronger knots don't seem relevant, since they would invariably cause the tippet to break at the blood knot. I hate having to tie on a new tippet every time I lose a fly.

Sincerely,

Salmo g.