I’ve always used webbing for setting up top rope anchors, but recently I’ve investigated using cord instead of webbing. For one thing, knots are easier to undo in cord then in webbing after being loaded. But is there any difference in strength between knots in cord and knots in webbing?

Interesting to see that a knot (Bowline of figure 8) will introduce a weakening to 73% of cord tensile strength.

Maybe more interesting is that in webbing, a water (overhand) knot degrades the strength much more then a figure 8 knot. Water (overhand) Knot gives a 57% of webbing tensile strength, while a figure 8 gives similar to a cord figure 8, at 71% of webbing tensile strength.

http://www.bethandevans.com/load.htm