This is saying the obvious, but Ward Fowler is William Shatner getting to PLAY William Shatner, because he's not only playing an actor but probably one who's considered a real ham (I don't know if Ward is ever actually called that, but that's probably the idea). Nowadays he's associated just about completely with those parodies of himself, but Ward Fowler is a very early case of something like that.
I think Shatner was lucky to get two turns as a murderer opposite Peter Falk. I'd take "Fade Into Murder" easily over "Butterfly..." as I'm more prone to picking the original series' run over the ABC run that started in 1989. I also thought it was original to have Ward speak to Columbo as Det. Lucerne and openly suggest to Columbo that Ward is a suspect. Throw in a young Shera Danese and Shatner's Star Trek buddy Chekov as Sgt. Johnston, and it's not a bad episode.
Probably Butterfly, it hd an interesting murder set up, where the killer is supposedlyat home on the phone
but is actually standing behind the victim, the first openly gay character, Molly Hagen from Herman's Head and another interesting thing where the cops out cycling disable the car.