One thing I never got was what did the title mean? In the context of the episode who or what was getting the Best of Both Worlds?
Especially with TNG which was probably the winner of the Most Boring Title award (90% of their titles were either one word or The [Noun]). It always seemed odd they went with something more poetic here but it didn’t make sense.
Never really thought about it before, but just off the top of my head I’d say it referred to Capt Picard, i.e. he was both an exemplary Starfleet Officer and a ruthlessly effective Borg drone. IOW he was the best in both worlds…
Because most of TNG were TV writers and a lot to TOS was written by sci-fi writers.
As for the title, that question is often asked. All I can think of is 'something to with Picard being both of best worlds.!
Picard was in two worlds, Starfleet and Borg. The writers needed a title. “The Best of Both Worlds” is a commonly known phrase.
People didn’t pay much attention to TV episode titles in those days. Frequently, only perfunctory contemplation was put into them.
Also note that, when the episode was christened, at best the events of the first part had been worked out. There’s not much to go on there except Picard being Borgified.
And calling the episode “Locutus of Borg” seems too simple. You’ve got to make it sound like it had more depth.
Remember how the Borg always said, “We will add your biological and technological distinctiveness to our own.” See, the best of both worlds.
He also rose to fairly prominent positions in both Federation and Borg society which is pretty damn hard to do considering those societies are by and large egalitarian.
And, specifically, it was a combination of human ingenuity (or just desperation) and Borg insider knowledge which eventually defeated them.
They could have titled the eps like Friends.
This one would be: The one with Picard as a Borg
The One Where Picard is a Borg, or
The One Where Picard gets assimilated, or
The One Where Riker Gets a Command, or
The One With The Sleep, Data.
That’s what I always took it to mean.
And as a follow up to that, I have always felt that the Borg Queen did not exist before the Borg defeat. It was always stated that the Borg adapt to threats (like the shields becoming ineffective after a while). The Borg had always been able to win with their unified hive mind and no specific leader, but when they lost to a hierarchical command structure, they decided they needed to add a form of that distinctiveness to their collective. That was their adaptation to the new threat.
The Borg Queen was the Borg’s own version of the ‘best of both worlds’. A being that is both part of the hive, and also an individual.
Plus, if Picard attempted to relate to her as an individual, so much better for the Borg. Having a ‘queen’ could fool humans into thinking of them like individuals. That the humans think that the Borg have a ‘leader’ is a mistake could be exploited by a clever plan.
The problem with that theory is that in First Contact, Picard says he remembered Her Majesty from his time as Locutus.
Picard said specifically in First Contact that he remembered her specifically - otherwise, I like your theory.
The writers messed up. 
Since he’s still in partial contact with the collective, maybe his memory is faulty? Otherwise, yeah, it’s there in the dialog.
Writers? You’re not saying the historical records have been tampered with, are you?
By Grabthar’s Hammer…