In my own opinion, the best knot depends on the type of fishing line that you are using. I find (and the manufacture suggests) that Fireline does not hold well when you are using knots which involve wrapping the line around itself. The manufacturer suggests that when using Fireline the polamor knot is the best option, and it is very easy to tie as well.
Been using exclusively FireLine since we could buy it in Michigan, all i use is the trilene knot, but i go around one more time, If you don't it is such a hard line it can slip, the key is one more wrap. That's all i do and it has never failed, plus make sure it's tight upon bearing down on the knot, than hold the line and yank on the lure.