Well, now that the surveys are out, lemme make this post talking bout the pros and cons of picking whichever first, aswell as trends you can potentially see happen, cause and effect etc etc. This is probably going to be long as hell soo lets get it.
Lets start with the dog first
not because finding a good ss caly-g sprite is harder or anything. First of all, this pokemon being disgusting is generally undisputed. However, i still wanna talk about the winners and losers of the ban of this pokemon, since this pokemon is extremely constricting. echoing what Basedwhat said, picking wrong against Zacian is quite literally fatal, and a Zacian with good play literally 6-0s every team under no exceptions. There is not a single pokemon in the game that can live 2 hits on a correct call and force it out, let alone living 1. The fact that alot teams use Ho-oh, Tangrowth AND Dusk mane for this pokemon nearly primarily is one of the most disgusting things i've witnessed in any metagame. It's no question i want it to go but if i want it to go first i dont know. Regardless let me post some of the winners the suspect would have for this stupid mutt.
THE WINNERS
I heard ya'll liked dragon types? Most all of these dragons appreciate the fact that Zacian isnt constantly threatening them out upon most occasions. While i know it's basic common sense that a fairy leaving will help the dragons, the two i left out from this list which i'll get to after, deserves their own paragraph personally, (spoilers, it's not reshiram lul) Giratina in particular shines from this as it's lard ass will always be forced out by Zacian without exceptions, as even a burned play rough is going to do a heavy chunk to it, banded or not. Zygarde also standsout as even with a coil boost it can't usually afford to stay in on it regardless, boosting the viability of the
war criminal set, so it's a winner. Palkia and kyurem-white usually don't run scarf so they don't ever have the ability to stay in on it. Eternatus is here as while it isn't weak to fairy Zacian genuinely doesn't care and neutralities are nowhere NEAR enough for it.
These two dragons benefit a little more indirectly, as they both appreciate the fact that when Zacian leaves Necrozma won't be atleast as forced on every damn team as before, especially not with a phys def set, Dialga benefits as it still has the ability to damn nuke offensive sets, which i think will become more popular, and also can be used more as a teams 2nd steel with teams not needing 3 zacian checks on their bloody balance team. Also specs draco is always a treat. Kyurem-black definitely benefits harder as not only is a natural enemy gone, Necrozma not running phys def means its way more effective at sweeping than it was before, and may be actually good again! Overall i found they deserved their own paragraph since they benefit from it's departure in more than just 1 way, and while zekrom has the same necrozma's a terrible zekrom check and you'll never change my mind on that.
Call me crazy but i think this thing would be the biggest winner from Zacian's departure. The sole fact that it isn't going to be commonly used as a terrible check for a broken mon it rarely beats anyway is a HUGE win for a mon as good as it is. Sp def, DD, SD, sub, this mon can start going into far more roles than being slapped on a team in the same core every single time a guy tries to build a good balance just to lose to xerneas. DD sets are nasty, and can run a similar set as before if it wants but with sp def evs instead for the stupid deer and our new Alien: Isolation crossover that we got this gen! While it will drop in usage most certainly is a downside, it being able to do other things more often that it's better at is just great for it.
Obviously we got most of the rest of the VR which benefits from it leaving in some fashion like Groudon, Buzzwole, Urshifu, Dracovish, Ttar, Zarude, i can go on. But most of them are just "FAIRY GONE LETS GOOOOO" or a faster threat is gone that it appreciates, so they don't deserve their paragraph but you get the picture. NOW for the losers, cuz surprisingly there are some!
THE LOSERS
These two metal birds greatest reason for use is as a good play rough switchin and with that taken away they really don't beat much besides offensive necrozma which is cool and all but switching into play rough is one of the things they are unparalelled at, so that going away is a blow. HOWEVER offensive Necrozma may be used heavily enough to the point where they may see use to mess with it, but for now i'm gonna say ya snooze ya lose. Go annoy OU cuz ya'll definitely do that too.
The Regen grasses also suffer, since alot of people use them alot because of how they atleast staved off Zacian, and while Tangrowth still has Groudon and Zekrom to parlay with, Amoongus doesn't really have that and i could see it going to UR potentially with its removal. (It's good at xerneas though, and spore is always nice.) But they can also lose if Zacian runs SD and/or psychic fangs, because remember folks, Zacian has no switchins.
I'm already out of losers wtf i hate this mon LMFAO. Anyway jokes aside, for my final verdict lemme list the things i can actually reasonably argue this mon brings to the tier without lying out my teeth because trust me it's hard, or any arguments that it should stay.
1) It beats down Zygarde. (I can't believe thats my best answer i can give man)
2) Another Fairy is cool. (I'm out of answers MAN)
Suffice to say, i think this mon is its own pandemic all it's own, whoever designed this pokemon on gamefreak's side actually deserves to be fired, it's way too broken, it doesn't look good atall, and it has no counters in the entire pokedex. Seriously though, this pokemon constricts the tier so so heavily it's truly unlike any pokemon i've ever seen before, and it's a pokemon that would've been quickbanned from ANY other tier at ANY other point simply off the effect it has on the builder. While i wanna see the metagame without it first almost certainly the boosts that caly-GG leaving kinda make me smile harder out of pure bias and nothing more, but thats a topic for another day.
ANYWAYS onto the horse, with celebi's bastard child riding it.
Personally not my pick for the first suspect, but i can agree that it's silly. Forcing a dark on alot of teams blows and the fact that it can muscle past the best one in the context of the rest of the meta definitely deserves some raised eyebrows, and i can't argue that. However i can say it definitely causes less restriction that Zacian does, and for that alone i feel Zacian should go first. HOWEVER that doesn't matter rn, since we got winners and losers to discuss!
THE WINNERS
Whoa, speed boosting sweepers benefit from the fastest relevant scarfer the franchise has ever seen is so WILD, who coulda predicted this1?!?! Jokes aside once again, Scarf Calyrex-Shadow often forced these pokemon out on unrevealed damage Calyrex simply because alot of the time it can just revenge kill all of them from like 80% aside from xerneas, and as for xerneas you gotta chip it for psyshock range but usually ppl drop their dusk manes for that, so it's not uncommon for that to common (Assuming ho-oh can't faze it) But generally these pokemon benefit hard from Calyrex-Shadow's removal so they definitely deserve their mention.
Sp def yveltal BLOWS in any other circumstance aside from Caly-GG, so seeing it go would open up all its offensive choices, which would be
broken as hell BLESSED, since who hates yveltal this mon is RAW, gen 6 really never missed on these boxarts. Correct opinions aside, this thing not needed to run trash ass sp def would be SO SO good for it, since it'll get to actually do whats its best at, like Necrozma, so it's a winner for the same reason.
DLC1 Flashbacks. This mon is best to reproduce the role Calyrex-shadow had as a ghost attacker, while still holding the defensive set above it. It has other tools to cripple Yveltal aswell such as Meteor beam, and could run scarf itself to do a similar role of revenge killing. It's plentitude of sets i think will find it rise to A rank at absolute minimum, this pokemon is really good and really only suffers from just better competition for most its sets.
The dogshit to ever so slightly rosier dogshit club for the fact that between Lunala and Caly-g you have NO reason to use them other than to flex. It'll probably still be the case after the ban but ay maybe i'll be wrong but these mons will likely stay ass, just less ass. but they do deserve i mention i guess.
Finally, the biggest winner i think the ban would have is Mewtwo. With both Calyrex and sp def yveltal fading away like they got vanquished by aggressive praying NPCS in Bravely default, this pokemon i truly think will rise to A rank. It holds so much variety, item and move choices that hasn't really gotten to be explored, but sets like Recover 3 attacks boots, NP 3 attacks life orb, taunt 3 attacks, 4 attacks specs trick, scarf trick, and alot of other options it has availlable to it, I'm confident it will rise to be one of the best metagame picks post ban, with its movepool granting options to pick and choose what it loses to, both team archetypes and pokemon.
THE LOSERS
The "I "beat" Calyrex and i'm not yveltal" club gonna be lucky to be ranked not named TTar. P2 was already terrible dont @ me and Zarude will lose one of it's best traits, condencing a zygarde and Caly check in 1. While it'll still beat Zygarde it won't be anywhere near as good as it was prior. Ttar atleast still has lunala and sand to be used on but tbh sand might just use hippo instead for zekrom.
The CEO's of the Sucker n Sneak club will miss being able to click their button and just kill Caly-BG, and thats a good part of their use. While not horribly hurt, they still appreciate their presence. Preying on lunala isnt as easy sadly, shoutout shadow shield. Grimmsnarl losing its niche as the screener who switches into caly sucks too since thats one of its greatest draws.
What does this thing bring to the table others cant? Well theres easily the BIGGEST thing in my eyes that the tier benefits from more than anything and almost makes me want it to stay is
CLERIC SUPPORT. By far the biggest thing that caly-g brings to the ubers tier is offensive cleric support thats fairly reliable to get off on choice sets from how much they force switches. It grants offense a way to clear status without using xerneas to do it which is so huge and something i've wanted for ubers for a long time. It also bringing zekrom and groudon revenge killing fairly easily with scarf is also a plus it brings to the table. Regardless though this post is WAY WAY WAY too long even for me, so let me get to my point.
Personally as much as i love Cleric support, i think suspecting either is fine, aslong as both are done. If Caly-G is done first, i think Zacian should be done in like a month after it, considering revenging with Caly is half the reason it isn't quite literally quickban worthy in my eyes. Regardless, do i expect my wish of Zacian going first? No, sadly not. However unlike Shadow tag, i won't be as up n arms over differing opinions because unlike shadow tag i don't fear the next suspect getting a no ban verdict LMAO. Either way, personally Zacian > Caly-G first but at the end of the day as long as both are done eventually i don't care.