To follow up on my posts about '60s sitcoms, Bernard Slade's autobiography, "Shared Laughter," describes the difference between the way sitcoms were produced in the '60s and the way they've been produced from the early '70s onward. Unfortunately I don't have the book in front of me for an exact quote, but the gist of it is, in my own words and with my own embellishments:
'60s shows carried very few full-time staff writers -- there was a writer-producer, and another writer as the story editor, and that's about it. Most of the scripts were written by freelancers. Once the script had been written, it would go to the story editor for a rewrite and polish, but once the script went into production, there was almost no re-writing.
The system on sitcoms since "All in the Family" has been more akin to the system on sketch comedy shows: a stable of staff writers who re-write every script collectively, and continue re-writing it all through the production process. This is partly a function of the live-audience way of shooting, but not entirely; "The Dick Van Dyke Show" was a live-audience show that operated with a small staff, and "The Simpsons" has no audience (obviously) and a gigantic writing staff.
Slade doesn't write about this, but the change in staffing procedures has changed the nature of the titles; the job of "executive producer" is now a combination of several different jobs on the '60s shows (sort of a fusion of producer, executive producer and story editor), while the "story editor" isn't actually the one in charge of editing the stories.
As to what's the better system, I couldn't say; Slade reasonably says that while the '60s way may not have produced better results than the staff-writing system, it didn't produce results that were any worse.
The one thing that we can say about '60s sitcoms is that, because of the less extensive re-writing process and smaller writing staffs, a sitcom episode of the period (or any TV episode, really) has more of the individual writer's voice in it than we're used to today. Of course, the staff would re-write a freelancer's script to bring it more in line with the overall tone of the show, just like today, but even in a re-written script there would be fewer contributors than in the age of the gargantuan staff, where dozens of different writers contribute to the same episode.
If I could bring up the first "Bewitched" season one more time (largely because there are so many good online resources on this particular series), the "scripts and their differences" websites includes an interesting example of how a freelance script could be re-vamped into something different by the staff. The site has a description of the development of episode # 21, which started as a freelance script by Anthony Wilson about a cat being transformed into a woman. The script was completely rewritten by one of the show's two writer-producers, Jerry Davis, with even the name and breed of the cat being changed. The site has a synopsis of the original freelance script followed by a synopsis of the episode that emerged, and it's interesting to see how every change makes the story less predictable, more tied to the idea of what a cat would act like if it became human, and more focused on the main character. The original freelance script actually reads, in synopsis, like something the show might have done in its later seasons, which, I suppose, is the potential danger of the freelancers-first system: without a strong guiding hand behind the re-writes, the scripts can wind up being by-the-numbers formula stories.
Then, of course, there's the most famous '60s re-write of all, the re-writing of Harlan Ellison's script for the "Star Trek" episode "The City on the Edge of Forever." Ellison tried to portray this as a slap in the face to his vision, but obviously what went on is that the script had to be tweaked to fit in more with what the characters would or would not do -- the sort of re-writing that only the staffers can do authoritatively.