Thanks, Bill. I guess I should have googled that first....
The website actually has numerical specs on the stuff, which is rather surprising for a product that you often seen sold in little trays next to cash registers at hardware stores. When you say that the Kwik is about as half as strong as the regular, I think the spec you are referring to is the tensile strength.
http://jbweld.net/products/jbweld.php
But in my case, it looks like the weld made a clean break from the tank. The JB Weld itself didn't break apart, it just separated from the tank. To me, that seems more related to the "adhesion" spec also listed on the website, and unfortunately, both the Kwik and regular versions are the same in that regard. But maybe I'm interpreting those terms incorrectly.
Dave