Both glues seem to be 2-part epoxy, but is one much better than the other? I know JB Weld contains metal dust, but does that really add much to the strength - I suppose it's a bit like the gravel in concrete...?
It really comes down to purpose. I love JB weld for making/repairing parts, and it's ability to handle high temps. However, I wouldn't use JB weld to glue wood, or wet out fibre glass. Araldite (slow) is more fluid and soaks into wood better, each has it's own character, as do all adhesives.
It's a bit more complex than that - just as, say, Copydex has less holding power than superglue, so different epoxy resins will have different strengths and weaknesses. Indeed - the Araldite you can buy over the counter represents just a fraction of the entire range...most of which is only available in commercial sized packs.
JB-Weld sets harder, and has enhanced tenacity ( i.e. it sticks better ). However, you can get superior capillary action from Araldite if you gently heat it, which makes it better at getting into small cracks. I don't know whether the particles in JB-Weld make any difference to its strength - I suspect it's more about making the final product roughly match its surroundings.
The Araldite you get in shops in two small tubes or a double syringe is simply crap compared to any fresh "proper" epoxy - West, NHP, Fibretech, Aeropoxy, SP or the like, take your pick - whether for glueing or laminating.
I have written this before, but if you have only used Araldite, and then get a fresh supply of a good epoxy - you will simply not believe they are the same stuff.
I haven't used JBWeld, so I can't comment.
I mostly use NHP for glueing and West for laminating, and I use quite a lot of epoxy - there are some better ones, but those are good value and work extremely well.
No comparison to Araldite, it isn't even in the competition, never mind the same league.
Also, Araldite can be given much greater strength by not just warming it, but by really heating it. The old data sheets used to quote increases gained at various times at various elevated temperatutes. The only determining factor is the progressive darkening with higher temperatures, upto the point at which it starts to char.
I imagine that that is how Ciba were able to demonstrate a 15 ton Ciba tanker, suspended from a 1" square lap joint in a 1" steel strap hung from a crane.
Also, there were many industrial liquid Araldites, not available on the public market, due to the danger of allergic skin reaction . A friend used some from work to repair a Hoover floor polisher, and also to laminate - with paper and wire - a firewall for the Microplas car body he was fitting to a Buckler space-frame chassis. This was over 50 years ago.......
I don't know about the current supplier/maker of domestic Araldite, but the original - made by Aero Research Ltd., and bought by CIBA was a good high strength wood and metal glue, developed from their wartime research into high strength wood glues - e.g. Redux (Resorcinol/formaldehyde) that were used to build the Mosquito twin engined bombers
I used to rebuild laminated wooden squash racquets - Dunlop Maxply ones, that had been smashed and dumped in the bin at the club I used to play at. I used two-pack CIBA Araldite, and layers of 1millimetre hardwood 3-ply (birch or ash?) - the stuff used in model aero making, a lovely material. The damaged plies in the racquet were removed, and new ones of the 3-ply tongued in, liberally coated with Araldite, and all bound up tightly with copper wire before being baked at a moderate heat. When cool and hard, the wires were stripped off, the glue and wood trued up for shape, the stringing holes reformed, varnished and the finished job taken to the Harris's Sports Shop branch at the club. There the manager would lean the frame against the shop wall, and press on it with all his weight! If it passed this test, he would have it restrung. I still have a couple that I kept, but many were rebuilt for their owners, after they discovered the saving!