There's a monogen tournament going on close to me and I obviously wanna win it, I know my shit about competitive but I can't decide on which generation to pick. Should I go Kanto, Johto, Hoenn, Sinnoh, Unova or Kalos?

Worth of note:

Doubles 6 vs 6
Item Clause
All legends banned

So, what should I use /vp/? Which generation do you think has the make for the strongest possible team?