The trick with superglue is to make sure you have a really good contact between two clean surfaces. If you don't have that, superglue will do nothing for you and you're better off with something else. If you do, it's quite strong.
The annoying thing is, glues work best when you use them in the exact situation (material, pressure, etc) they are designed for, but manufacturers are really vague about active ingredients or fillers, so you end up having to buy broad-spectrum glues that are not particularly good at anything.
I've had good luck with super glue when roughing and recleaning the interface surfaces. That said, cyanoacrylate (?) does seem to have sudden fracture failure, e.g. cracking.
When in doubt, I'm a firm believer in two part epoxy [0]. Fiberglass impregnated when necessary. Also stores easier!
And where water is involved (e.g. fiberglass shower tubs), marine epoxy like PC-11 [1]. Can attest it works fine as a multi-year shower patch.
The annoying thing is, glues work best when you use them in the exact situation (material, pressure, etc) they are designed for, but manufacturers are really vague about active ingredients or fillers, so you end up having to buy broad-spectrum glues that are not particularly good at anything.