I've been a J-B Weld user for many years and it's worked well for my applications.
I recently saw a test on YouTube comparing 6 different epoxies.
https://www.youtube.com/watch?v=bM4IGweHT2k 4" cap screws with 3/8" heads were glued to an aluminum bar and both surfaces were prepared with sandblasting.
This test was a high leverage test, hanging different weights at the end of the bolts and increasing the weight until failure, although none of my applications had that kind of leverage applied.
Obviously the test didn't have the precision of a more carefully controlled laboratory test, but it was still interesting nonetheless.
I haven't used J-B Weld in some of the extreme applications mentioned by the manufacturer, such as gluing together a tractor hitch or an engine block. I'm a bit skeptical of those, particularly the engine block scenario where high heat is involved.
I do like the dual syringe applicators that result in a more accurate mixing ratio with less waste.
Steve