Wherever possible, zero-touch offers the best experience both for organisations and users. For organisations, it provides not only the decreased overhead of not having to explain how to manually start provisioning a device (and the support required when users still don’t get it), but also the confidence of knowing should a device be factory reset accidentally or with intent, the device will jump back into zero-touch provisioning as soon as it’s connected to a network. This extends to Samsung’s KME equally for the same reasons. That doesn’t mean zero-touch is the fastest and most efficient provisioning method, in fact it’s probably comparable in speed to DPC identifier, however speed is but one consideration.
If zero-touch isn’t available, my personal preference is QR code provisioning as QR codes are persistent (normally), can be hosted anywhere or freely shared between employees, don’t need a dedicated provisioning device, and support DPC extras.