It's been a long time since I've broken a fish off. I can't help to think it's because of the knot more than the line. The strongest knots are hands down the palomar or trilene knots. The clinch knot is inferior to the trilene knot as the trilene knot doubles the line through the eye. I think this is critical in a really good knot. As for the palomar, it's easier to tie, and it never slips no matter what.
A trilene knot is a clinch knot with the line doubled through the eye, and the tag passed through the double formed loop. I use 4 twists for mono and 5 twists for flourocarbon.
The palomar is basically a loop created at the end of your tippet, with the loop passed through the eye, with a simple overhand knot tied and the formed loop passed over back around the hook. Very easy and quick tie. Youtube them if you wanna try em out.