Hot take but I think there's some truth to this for both series. I feel like some cases of Berserk utilizing rape aren't as meaningful as other cases in the series and I think SAO's use of rape isn't as egregiously offensive as many make it out to be. https://twitter.com/jayphoenixtv/status/1252103856231796737

SAO uses rape to show the antagonists are bad in a pretty basic, straightforward way that doesn't make them interesting characters but it gets the job done in order to make you viscerally hate them. This is similar to Berserk demons and trolls who have no motives outside rape.

In these cases, there's no fundamental difference between either shows use of rape to make you fundamentally hate the antagonists without further characterization. The difference between Berserk and SAO lies in how the former portrays rape that characterizes the main characters.

Guts' rape as a child fundamentally changed his life and made him a closed off, emotionally distant person, who loathes human contact. Griffith raping Casca scarred her for life while showing the true range of his villainous actions against his closest comrades. While also...

...giving him the vessel for his rebirth into the mortal world. So you could argue this rape had a fundamental narrative purpose outside of showing Griffith's villainy.

We don't get to see the negative emotional effects of rape/assault on the SAO characters, at least in the anime adaptations I've seen, which is why I understand the criticism that it utilizes rape too lightly.

On a surface level, Berserk and SAO both use rape to make you hate simple antagonists BUT Berserk also shows that rape results in long lasting emotional trauma for our main characters that they have to constantly fight to move on from, and that's praise worthy.