I used eMMC.
When using eMMC it is not easy to flash back to an initial state.
I need to use an USB A to A cable and the RKflasher tool.
Once configured to boot from eMMC you can not easily boot from SD Card again.
I haven't tried the option to erase the initial portion of the boot section, this may also work instead of USB recovery. Hence I am familiar with USB recovery I just use it.