The biggest differences are in the main campaign quest. You fight most of the same bosses, but otherwise almost every quest is different, including the reasons and methods of fighting said bosses.
In terms of side quests, I got the most satisfaction out of the character-specific chain quests, that flesh out your character's backstory and motivation based on your alignment.
In terms of the more generic side quests, there are some that remain the same, some that are changed, and some that are only available depending on your alignment.
F1ach: Yes, I get that, two of my favourite devs are Larian and Ascaron, they really put a lot of heart into their games :)
Totally agree, and I'd add CD Projekt Red to that.