Vvdi2 for bmw and vag vehicles, esp good for immo
Vvdi prog reads ic chip called eeprom. And write it back
In the end you’ll need both if you want to have a complete solution.
Just to give you a practical example, some CAS Systems like CAS3++ for some reason VVDI2 or any other programming tool won’t be able to flash it in order to make a key for it.
This is when VVDIPROG comes in handy and allows you to read EEPROM and Flash to have a backup in case something happen and also to create a dealer key in order to complete the job.
Just to be clear you only need EEPROM to create the dealer key but having both files allows you to restore the whole unit in case of any issue during programming.
My advice is to always make a full backup and even being this careful you can run into trouble and always use a voltage stabilizer while making any change on vehicles modules.