What stands out with Dirty John compared to both or either of the Serial seasons was the payoff at the end. Serial season 1 was intriguing and well done, but really, it's another story about somebody convicted of murder and we don't really know who did it. There's no reveal at the end of the season with a confession or a new arrest. Sure shit gets weird, but not like bad guy trying to murder the daughter of the wife to get revenge on her and end up getting stabbed through the eyeball.
Same with season 2 of Serial. Beau was a dumbass who deserted his squad. The payoff was pretty decent when he escapes and makes it through the desert etc. but I had a hard time trusting anything that guy said.
I'm listening to True Crime podcasts now, each story has 2-4 episodes. There's a shit ton of episodes already broadcast too. For stories like these it makes a HUGE difference having a great narrator. It's just something about a voice like Koenig or the guy from Dirty John that draw you in. Some of these stories are quite epic as well.