Much as I love Dexter as it is, I'd definitely love some more moral ambiguity - something I feel has been stripped away, if anything, as of late. When the show began, Dexter killed primarily to satisfy his compulsive, innate need to kill. The positive social effects in removing a criminal from the streets was more incidental. Now, since becoming more of a family man, his desire to kill seems to be primarily driven more by concern for the victims/potential victims of his targets, rather than simply to satisfy his own "dark passenger". It's been a subtle shift, but I feel it has taken away some of the ambiguity around Dexter as a character.
I've never watched Breaking Bad (though about 239587 people have told me to start), so I can't comment there.