Since the late 1960s, I have used the whipped loop knot, made with size A tying thread and a bobbin. Instructions can be found in the book Practical Fishing Knots. With a little practice, this knot can be installed in both ends of the line in minutes, and it will be stronger than the line - I have never had it fail. Also, the whipped loop tapers smoothly to the line, so it can't catch on the guides. Making the loop with two nail knots to hold it in place, as many prefer, requires the tier to take extra care to ensure a smooth connection that won't catch.