Comparing the documentation for the new Catenate function and the updated Join function, the pros-and-cons aren't immediately clear. They both operate on both Lists and Associations, and both do approximately the same things, though the syntax is different (Catenate takes a list of arguments, Join takes a sequence). I'd be grateful for some use cases for the two that highlight similarities and differences so that I'd have some guidance about when to choose one over the other. Documentation is found in the Documentation Center under the following paths:

ref/Catenate
ref/Join