Pros: more comfort, more colors to choose from, improves the sounds .
The Yaxi pads are a vast improvement over the stock tiny black pads that come with the Koss porta pros.
The Yaxi pads offer a much more comfortable fit and reduce clamping pressure.
In addition to that they provide a cleaner sound cleaning up the bass and mids and the treble. They enhance the sound and details IMO and are a inexpensive way to upgrade your headphones look and sound.