In the case of just 1 system and no upgrade to the Premium Edition they are equivalent. The Rescue Disk requires an external hard drive and the Factory Backup requires a USB flash drive. I have not tried a SD card for a Factory Backup just a Bootable USB for Factory Backup. The Rescue Disk is the same as the Factory Backup with the exception you can use 1 external drive to make factory settings for up to 10 Dell systems... If you use the Premium Edition you can get more advanced features like making a custom backup and can set it to continuously backup data. 
I just purchased and set up an Inspiron 3847 with Windows 8.1 and I have tried to create the factory backup and restore DVDs but the procedure  has ended with an error twice.    It seems to get to the end (ie. 2 seconds left) and then gives me the error indication.  It looks like it should try to verify the DVDs but it never gets to that step.  Does anyone know what gives?  Is the set of DVDs bad?
Dell Backup and Restore ends in error