but there's nonetheless a difference surely not in principle because anything that's been written may be read out and spoken (and viceversa, anything is potent

but there's nonetheless a difference surely not in principle because anything that's been written may be read out and spoken (and viceversa, anything is potentially transcribe-able) nonetheless, when push comes to shove there's a real difference: written stuff (text) is readily usable as evidence but things only ever spoken are not.