Both PySide2 and PyQt5 have a commercial license that you can purchase from their respective owners.
The primary difference is in their non-commercial licensing, PySide2 is primarily licenses under the LGPL (some bits are GPL) while PyQt5 is 100% GPL.
There are also probably some minor API and stability issues as well, but I’ve been out of the comparison game so I’ve lost track of what those are.