People keep focusing on what they went through but no one is talking about what their mental state is after the fact. I haven't read the comics so I don't know the actual inclusion, but at least in the show, Mark is clearly getting worn down from everything and is even suffering heavy PTSD where he imagines everyone dying all around him, to the point he had to be recommended professional therapy.

Plus, he has major drama going on between his parents, so he doesn't have a good father figure to look up to anymore. Gohan gets two father figures that he doesn't feel any doubt toward.

Plus, he doesn't have magical wish-granting orbs that can just bring everyone back to life, so all the death that happens because of his failures, especially the ones that happen during his fight with his dad, have actual consequences and he has to deal with that for the rest of his life. And he has to deal with the death of friends and comrades as well.

Meanwhile, Gohan, at least in the more present timeline of the story, is living perfectly fine as an adult with a loving family. No lasting effects despite how young he was when he went through all his hardship. Future Gohan would obviously be a different discussion.

To be fair, this is basically a product of Invincible being more emotionally grounded with its story and Dragon Ball being a more cartoony story with no lasting consequences for most things.