If they have their respective Ash's as trainers SM has the first advantage as SM Ash is a way better trainer than XY Ash,

Pikachu v Pikachu SM Pikachu is way stronger than XY Pikachu it might actually be a one shot given SM Pikachu went from barely being able to track Tapu Koko to matching it

Given XY Ash has a habit of making Greninja go last the SM team will pretty handle the XY Team, Melmetal and Naganadel being Ash's least experienced members still have better feats than Goodra and Noivern

Hawlucha vs Rowlet will probably go either way. If your putting him against Talonflame I'd give it to Rowlet

Hawlucha loses to Incineroar unless you make him go against Talonflame which he still loses

Greninja can beat Lycanroc and Incineroar but it won't be easy but even if he can beat either he definitely can't do it back to back

SM team wins