I don't perceive Jack and Angel's choices as being comparable. Because Connor was not going to be killed, he could have been saved another or dealt with another way. Also Connor had murdered numerous people, he was a murderer. He wasn't an innocent child. It wasn't an either save Connor or save the World.

Angel's choice wasn't the same as Buffy's regarding Dawn in the gift. Dawn, a)was an innocent, b) she hadn't murdered or hurt anyone. Also Buffy had the world at stake - she sacrificed her life to save an innocent child and her world. Angel manipulated and brutally hurt others to save a mass-murderer because the boy was his son. If Connor had been anyone else, Angel would have killed him.

Re Children of Earth? I hunted down my review of the series...this was back when it aired.

http://shadowkat67.livejournal.com/450878.html

and here:

http://shadowkat67.livejournal.com/450602.html

Both Jack and Angel are monsterous in different ways. I looked at Children of Earth from a different angle.