Yes it is nice to be able to put your projects INSIDE something isn't it? You know, to hold everything together so it doesn't flop around? Discuss the techniques here!
One part is resin, and the other hardener, so I'm assuming it's basically the same thing. Tough as rock, and only breaks if you pull hard. However it's brittle. Although it's hard enough that it would only crack if dropped from a height or hit by an equivalent force. On the other hand, hot glue will bend and remain glued to the surfaces, but won't provide good structural support (because it can bend).
This depends on what type of material you're using, but for general plastic-to-plastic bonding, "plastic welder" epoxy gets my vote for sure. It dries an ugly cream color though. There's also your standard 2-ton epoxy that dries clear, and it's pretty darn strong, but lack that certain "holy crap!" strength that the plastic welder has. (Comes in a black syringe).
Hot glue...
Please, for the sake of the future of all mankind, don't use hot glue to hold your case together. Pinning down loose wires and other various components INSIDE the case? Fine. But holding the casing itself together? Oh hell no.