The crape myrtle boasts the big flowers that grow in panicles (lots of flowers on a many branched structure) . The wax myrtle hosts inconspicuous blooms. A bigger issue: crape vs. crepe? I think crepe says something about (like) pancakes, paper and neck skin. Crape is for the tree. Almost everyone (like dictionaries and wikipedia) says so*.
We know how the Crape Myrtle Society of America do. Who don't? Southern Living.