Ability to make you own art, stand or fail!!!!!
Seriously, though, the difference between some full sessions and other is how abrupt are the cutoffs. I really do like hearing the players voices, hearing their speech timbres and inflections. To me, that's a part of how they play, how they talk, that and their temperment, are the snappy or quiet, what kind of people were they bringing to their playing etc.
That's why I love those talking records of The Lion, Hawk, Jo Jones, etc. Chico Hamilton. Lester! Yes, music is enough, but music is not all.