Version 15.1 wasn't just a minor patch; it brought several quality-of-life improvements:
: For enterprise environments requiring silent or bulk deployment, MSI installers are available under the "Special Installations Only" section of the support portal. Key Features and Improvements in 15.1 toad for oracle 15.1 download
: If you already have a commercial license, you can download the 15.1 installer directly from the Quest Support Portal Version 15