nothing in terms of functionality to gain
but if you do it you can unplug your usb as 6.2.2 is still runing, put the new extra/extra2 to the usb replacing the old, plug it back and install 6.2.3 through the gui
(its also possible to mount the usb, while still plunged in, on dsm 6.2.2 running, copy the extra/extra2 to it, unmount the usb and then do the update to 6.2.3)