Petras seems like a dick, since he was talking about how he wants to murder someone first thing after the mass.

But Dal doesn't seem so bad. She seemed concerned about the well being of her "brother" when Ast was threatening him, and she also sounded worried for Ast when he comes back and says in a hopeful tone that he was free, why would he come back. As in, she considers freedom from all this to be worthwhile. So while her peer is thinking about who he's going to eat, her thoughts are about just escaping all this.

We know she killed a child, but if you read the journals, she's a doctor and she had a theory about how to cure vampirism that involved a child's blood, and since she's not in a lab setting she took the only source. Obviously we're not excusing her for this sin, but it wasn't wanton murder or self gain, and she wouldn't have done it if she could get a sample in a more humane way.

I think Petras is an example of someone who was changed by the experience, and his desire is to be the big guy vampire some day and he's a spawn in the meantime. But Dal seems to be an alright person in a bad situation. I also find it interesting that Ast is basically right in between them, at a crossroads, where he can be driven down either of their paths depending on the player's choices. You can either make him worse by ascending him and he becomes the bad guy who induulges in vampirism (Petras), or you can make him better by getting his neutral ending, where he values freedom (Dal).

I think bg3 is a pretty cool game.