It's a lot like when Tony Randall and Jack Klugman insisted THE ODD COUPLE switch from single-camera with just a laugh track to multi-camera in front of a live audience: both of their performances certainly have a lot more life, enthusiam, and charisma when the show had a live audience as opposed to their more reserved their performances were during their single-camera season. Tony as Felix, in particular, can be really hammy and animated at times, but that just further adds to the neurotic personality the character was supposed to have anyway.That's why it's often easy to spot a stage actor in a movie or TV show, they're using a different style.
It's ironic, because I usually have a stronger preference for the more cinematic approach that single-camera sitcoms had back in those days, but switching to multi-camera in front of an audience really brought THE ODD COUPLE to life; I'm not saying the first single-camera season was bad, but it felt pretty generic and bland compared to ensuing seasons.