The interesting difference is in the attitude of the two networks. NBC handled Star Trek and Roddenberry their own way, but CBS and Paramount, in their frustration over the money spent, wound up installing Bruce Lansbury as producer in place of Bruce Geller, who disregarded budgets completely (in contrast to the Trek staff tried very hard to spend wisely). Lansbury was a "company man" and brought in solid shows responsibly (he proved his worth on Wild Wild West), but the cast and crew were loyal to Geller.
Over at NBC, when Roddenberry was on the way out, Freiberger was, apparently, his own choice to line produce. It makes me wonder if Trek were on CBS, would the network or Paramount had taken steps to keep the series going with their own producer choices. Of course, I'm sure the overall ratings difference had a lot to do with it.