MT-6000 Flash back to OEM

If this has already been answered, I searched before posting
I'm new to openwrt, I have flashed other routers in the past with dd-wrt, with great results.
Question I have ?
I flashed my MT-6000 with openwrt sys upgrade (24.10.1) if I want to go back to original Firmware, do I use same method sys upgrade to flash back or use the uboot un brick method. I've read all over the net, seem's both ways are dooable, not surewhich one is the right way.