No we do not know for certain what Stooge product quality would be like with different third stooges. But your post prompted another thought. With Mr. Besser in the Stooges, might have TV executives have given more thought to a weekly series - you see, I lived through that era as a kid and my memory from the 1960s of Joe Besser just does not jive with much of what I see posted on this site.
My childhood friends and I all picked Curly as our top Stooge. But nobody berated Besser. In fact, maybe I was in a weird group of kids, but we all thought Besser was funny on his own as well as with the Stooges. When Besser turned up on Joey Bishop, my friends and I watched that show whenever the parents allowed it. When my friends and I would see a TV ad that Besser was about to appear as a guest on one show or another, each of us would notify the other that former Stooge Besser would be on the show. Even back then, unless my memory is playing tricks on me, my friends and I wished that Besser was in the Stooges instead of De Rita. None of us ever gave Joe the same credit as Curly or Shemp – that would have been sacrilegious! But we did think Joe was funny in his own way and we liked him. In my San Jose, CA grammar school in the early 1960s, the words, “not so hard” could be heard at the appropriate funny moment quite often.
Returning to my speculation in the first paragraph, my memory of Joe combined with what I know of the 1960s TV landscape makes me believe there were plenty of TV decision makers that thought Joe Besser was funny and/or a likable character for TV audiences. The evidence for that is Joe was on so many shows in that era. If Besser stayed with the Stooges through the 1960s, maybe an offer might have come for them to do the “shorts” format as a weekly series. I suspect DeRita was looked at by everyone except Moe in the 1960s TV industry as being washed up. Thus no offer of a weekly series was ever thought about, let alone offered to our boys.
Finally, as long as Moe and their producers/directors of their 1960s movies were willing to kowtow to the PTAs and others that wanted the violence toned down in their projects, you are correct – Besser would have made little difference to their movies. Unless a different sort of comedy was written for the team due to the presence of a third stooge with a personality – Besser. I cannot even detect what sort of a personality DeRita had. With DeRita, the writers tried to recreate the Curly era, but without the talent of Curly nor the will to do the hard slapstick (or farcical comedy as Moe apparently put it). The presence of Besser might have prompted a different approach to the scripts because I suspect the movies writers would not have tried to peg Joe into the Curly mold the same way they tried to peg DeRita.
Anyway thanks to the people who maintain this site. It is great to have a forum like this where we can appear serious, but remain light hearted, about our not so serious objects of our affection, The Three Stooges.