The Expander is a Plug-In for use with Logic Audio which is an expander with a ratio range from 1:1 to 0.5:1. It also has the very helpful autogain circuit.
The Emagic Expander is a true upward expander featuring a ratio range from 1:1 to 0.5:1. The parameter set was adapted entirely from the compressor - including the very helpful autogain circuit. Sure, an expander is one of the more rarely used dynamic effects, but in some cases it is the only tool for the job.