The key thing to remember when choosing an adhesive for a particular job is that there is no substitute for physical testing. Adhesive manufacturers perform extensive test protocols on substrates and provide empirical data in the form of a Technical Data Sheet (TDS). Specifications for bond strength, cure speed, viscosity, basic physical properties and general information are listed in a typical TDS. An adhesive supplier may make a recommendation for a particular application that the end user should confirm using the Technical Data Sheet.
In a countertop application, the accepted test method for flexural strength is the ASTM D790 also referred to as the ISO 178. Basically, this is a three point break test that measures stress vs. strain or load vs. displacement to determine the flexural strength of a bonded butt joint. The lab prepares accurately cut specimens and bonds them together in a controlled environment, usually conditioning the bonded samples for a period of 24 hours before breaking them. The data obtained from breaking a large number of the bonded samples used to provide accurate flexural strength numbers and good guidance for the best uses of a particular formulation.
If you happen to have a substrate that no one can give you a recommendation for, you can do some simple testing yourself. The test that I use when comparing cartridge adhesives for strength from brand to brand is just a scaled up version of the three point break (without the accurate results). Prepare two samples of the substrate that you want to test in a size that will allow you to support the bonded joint between two points raised up off the floor. I usually use about a 4 inch wide strip, 24 inches long and then cut in half. Bond the 2 samples together, let them cure and then introduce weight incrementally until the joint fails. To get an idea of the bond strength you can then compare the results to an adhesive/substrate combination that you are already using. Even better, perform a side by side comparison.