The host personality is supposedly the dominant one, even if it's much younger.
The Symbiosis commission stacks the deck. They claim that only two percent of the population can Join successfully. It's actually %50. What does a bad join look like? Sure the personalities could collapse, and you're just looking at a mountain of sod instead of a person, as the worst case scenario, but where there's 98 ways out of a hundred that everything could go wrong, or it's 50 ways out of a hundred that every thing could go wrong, how do they define "wrong"? Maybe one of the other hosts takes over, or maybe the symbiont takes over? And why wouldn't they if they could, if the alternative is living death?
This is yet another wild theory with no basis in the show.
Well, Sisk did ask Verad Dax to consider this…And he said he was fine with Jadzia dying. And yes, this is an interesting insight into the symbiont's morality.
Anyway, I think that a much better Tuvix comparison is with Phage: here Janeway is tasked with a similar conundrum, saving a life at the expense of another, another that condamned Neelix to almost certain death (just like Veerad with Jadzia), yet she reaches the opposite decision (BEFORE the Viidians tell her they might be able to save Neelix after all). Perhaps all she cares about is numbers and saving two people at the expense of one is better than a one on one exchange?
Janeway's final argument to herself was Tuvok's wife T'Pel might be sad, even though Vulcans suppress their emotions, and she already thinks Tuvok is dead, and who in 70 years when their descendants get the ship home, will probably be dead herself.
You have a library card?
If you get the same book out 6 times, are the librarians going to say that you took the book out 6 times or once?
When Tom Riker rejoined Starfleet, should he have gotten Will Riker's rank?
Those weird people who remarry the same person again years after a terrible divorce, because they are different, and they are sure that they can make it work now.
The tenth Doctor died and half regenerated back into the tenth Doctor, and Donna, and a severed hand. Because his face didn't change, no one cared or thought that it counted to the final count of 12 regenerations, but it did, and he ran out of lives, and all seemed lost...