Sometimes faster. Basically it uses a roll back process like mib2 high. Turn the ignition off and it stops after 20 minutes. Has a restore point and starts next time... etc. Over the air takes a time, the 2-3 days. All depends on 4g and the Vag provider they use. USB faster.
I trick the mib2 high and have suggested this technique for mib3. You open the door every 15 minutes with the ignition off. Reason for that at 20 minutes it goes into power down and you get a restore point. So you can force it that way, straight threw without stopping. Why people like the usb with the LED on it so they know they have activity. Mib2 high I use the engineering menu so I visually see what's going on.
That's a standard trick retrofitters use, you can leave the door open and it won't time out. I return back to the house, twice
.
Nobody has told me that 15 minute trick doesn't work on mib3 yet. The whole process for European files should take circa 40 minutes. Dependent on the USB speed and the infotainment unit.