The second ones let the guests speak almost freely, or the hosts themselves are excited about a technology so much they would go into juicy details, and it's an amazing feeling as if you are not listening to an interview, but eavesdropping on a conversation between peers (which it often is). These aren't as frequent as I would love — for whatever reason podcasters tend to picture their audience as new and ignorant rather than experienced and knowledgeable. React Podcast's episode with Andrew Clark fell straight into this group. JS Party was in this category too (sadly, they stopped releasing new episodes... oh, wait, actually they are back). Toolsday belongs here as well. Web Platform Podcast varies from episode to episode. Frontend Happy Hour... perhaps. Magic Read Along definitely. Modern Web Platform I am not sure about, but that's because I can barely stand the host, Tracy Lee.
I wish the second group were larger.