This is a classic arduino firmware upgrade. This upgrade become easy with the help of Dagom'app software. Dagom'app detect the printer and insert the user in a user interface which leads to the flash of the arduino firmware. After, the printer works with the new firmware.
Unless you are 3d print specialist, the changes are almost invisible. What's you printed before works more or less like what's you plan to print or reprint.
From my point of view, I have the credo of working with updated system. That's why I have done the upgrade. It's interesting when you have a broken firmware or a 3d printer which fails or print the objects with drawback. The output of the arduino card plugged with a serial COM port shows very few changes or modifications.
To conclude, I can say that between the 2017 version and 2019 version, there is no major changes. We can see in the 6 first lines that the firmware shows the compilation date in slithly different way. For those who are interested below are the two outputs: