SysBlog

Using CFSet

Creating a copy of a Structure using CFSet will result in a new variable having a reference to the original Structure;
changes will affect the original Structure.

******************************************************

Using Duplicate

Creating a copy of a Structure using Duplicate will result in a new variable containing no reference to the original Structure but rather a snapshot of its current contents.
changes will NOT affect the original Structure.

******************************************************

Using Strcutcopy

Strcutcopy is where most people get confused.
We can say Structcopy is between CFSet and Duplicate.
When we use Structcopy, a new structure will be created; however, references to nested structures, objects, and query variables will be maintained from the original Structure.
changes will affect the original Structure.

******************************************************

Source: https://www.experts-exchange.com/articles/8971/Differences-in-Creating-Copy-of-a-Structure-Using-CFSet-Duplicate-and-Structcopy-in-ColdFusion.html