Both are apps from DVDFab. DVDFab itself is the larger of the two [~230MB download vs. ~37MB], including a large number of modules that can be purchased / activated separately -- we've been given Blu-ray copy & Smoother modules this year on GOTD. While you'll find some complaints in forums at VideoHelp & DVDFab sites, DVDFab works as you'd expect from a long time developed product. The copy module we were given does just what it says, copying the complete contents or just the main movie from a Blu-ray disc. Copying the main movie removes all menus -- if you want you can remake the Blu-ray [or a DVD] with your own simple menus using free or paid authoring software. Both apps phone home asking for instructions on how to handle the disc's DRM -- for some reason DVDFab seems to work in this respect on the rare occasions that Passkey cannot.
You don't get a GUI with Passkey -- instead it's more or less a driver that sits between the optical disc drive & Windows. When a DVD or Blu-ray disc is inserted you see a progress window just above the notification area on the right end of the Taskbar, showing the progress as Passkey phones home for a solution to the DRM. Once that's completed you have 2 choices -- you can play the disc in any player, including players that otherwise could not handle the DRM, e.g., VLC, or you can right click the taskbar icon and select to copy the entire disc to a hard disk. Passkey tells you which playlist is correct -- there may be a hundred or so playlists, some for menus & special features, and some that are fake. You can open that playlist in the free app, tsMuxeR, to copy just the main movie, along with your choice of audio & sub tracks, to another folder. [While you can copy just the main movie in DVDFab, you might still use tsMuxeR if the video is split between 2 or more files to give you a single video file, which works for players that do not understand DVDs or Blu-ray.] While it's still sold and developed, Passkey is a bit like an unwanted stepchild compared to the flagship DVDFab. It's a bit glitchy from time to time, and you'll get some impossible to ignore advertising for other DVDFab products.