IoA'd have more room than sharing SNW for sure and I'd take that, but at least my argument for pushing Zelda to EPIC is if despite IoA rumours it became necessary for it to have the larger expansion pad (plausible)
*and* Universal feels IoA would work better for their other top picks which are both about books and adventure then that outweighs other parameters.
Spreading Nintendo across all parks, keeping it all in EPIC, I would find to at least to the consumer those have equal yet distinct benefits. IMO the deciding factor should be which non-Nintendo IP maximizes it potential and synergy in a given park, because given enough room, Zelda works in either equally and Pokemon can go anywhere and sell its self with little space (albeit as a city based IP, Studios lacking a banger has a great pull here).
Having said that this is min-maxing, If its between Zelda, Pokemon, Wicked/Oz, and Lotr, once again besides space needed, its like trying to get a grade from an A to A+. The fact they'd all presumably exist in our assumed quality and any park combination makes up the bulk of the grade.
Luigi's Mansion isn't big enough to justify that entire expansion pad at Epic alone, so something else for Nintendo just makes sense.
I beg to differ

! but if worse to comes to worse, not only is there one other thing for Mario I think Nintendo can put there reasonably without needing to cramp in Zelda, I think its also entirely plausible with Dark Universe's success that it simply gets to steal a section of the expansion for itself. And once again there'd be absolutely no problem with LM and Universal Monster mixing, because that's kind of the point of putting LM over a more popular Nintendo IP. Don't get me wrong, I would have always chosen the GOAT regardless, but for big business brand synergy, I'm sure thats one of the strong reasons LM is on the docket.