The ideal option would have been to continue Palpatine's physical decay from AOTC (something Lucas backtracked on causing a continuity error) so that he just looks the way he does in ROTJ because that process has just brought him there.
However seeing as Lucas thought his audience too stupid to fill in the blanks themselves and had to show Vader wearing a more perfect and less interesting version of his OT costume and have the wrinkly Emperor by his side he went down the route of having the Force lightning blowback explanation which is daft as neither Anakin,Mace, Yoda or Luke receive any facial warping from the full blast of direct Force lightning but Palpatine does on the rebound.
The transition effect is rubbish so I don't mind losing it on a technical level either.
The only problem it leaves is why doesn't Palpatine restore his false face and how does he explain it if he can't?
The obvious answer being he can't for some reason and he lies about being the victim of a Jedi assassination attempt and scarred.
Which then makes it seem to make as much sense that he is scarred.
In the end it all rests on the editors ability to pull the effect off because no form of tinkering (that I've read or seen) can make the scene make narrative sense thanks to Lucas.