The Question of the Day is a way to facilitate community discussion to help members ponder the unanswered questions of the world that are somehow relating to the hobby. Questions are many times open ended and up to interpretation, followed by a related question. Feel free to post your thoughts in as much or as little detail as you’d like.
Helpful Considerations may or may not help some people focus their answer, these are blurred to not bother those who have their own ideas.
I want to say even if only because odd numbers feel more chaotic (3 and 7), but 5 is a perfect number that births the great even 10, 100, etc. (I know 3 and 7 make 10, but it’s an unholy matrimony)
Looking at just all Legendary and Mythical Pokémon:
Even - Legendary:
Articuno
Moltres
Mewtwo
Entei
Ho-Oh
Regice
Latias
Kyogre
Rayquaza
Uxie
Azelf
Palkia
Regigigas
Cresselia
Cobalion
Virizion
Thundurus
Zekrom
Kyurem
Xerneas
Zygarde
Type: Null
Tapu Lele
Tapu Fini
Cosmoem
Lunala
Zacian
Eternatus
Urshifu
Regieleki
Glastrier
Calyrex
Chien-Pao
Chi-Yu
Miraidon
Okidogi
Fezandipiti
Terapagos
Odd - Legendary:
Zapdos
Raikou
Suicune
Lugia
Regirock
Registeel
Latios
Groudon
Mesprit
Dialga
Heatran
Giratina
Terrakion
Tornadus
Reshiram
Landorus
Yveltal
Silvally
Tapu Koko
Tapu Bulu
Cosmog
Solgaleo
Zamazenta
Kubfu
Regidrago
Spectrier
Enamorus
Wo-Chien
Ting-Lu
Koraidon
Munkidori
Ogerpon
Even - Mythical:
Deoxys
Manaphy
Shaymin
Victini
Meloetta
Hoopa
Marshadow
Meltan
Odd - Mythical:
Mew
Celebi
Jirachi
Phione
Drakrai
Arceus
Keldeo
Genesect
Diancie
Volcanion
Magearna
Zeraora
Melmetal
Zarude
Pecharunt
Not sure if any kind of conclusion can be made with this split. I guess the odd mythical list is longer than the even one.
But, since the most crucial contributing factor to this battle is number #399, it’s obvious odd would win, should this battle ever occur (possibly resulting in a destroyed universe with a single being left standing to build it back up).
If we consider that there are 1025 pokemon, the first 1024 all take duels but that 1025 has no one to fight, so it can start cheap shotting pokemon from other fights and therefor making the whole fight unbalanced and leading odd team into victory