The biggest benefit of mega is bonus candy
Many players think the big benefit of a Mega Evolved Pokémon is that it gets stronger in raids. I think the biggest benefit is bonus candy instead. As long as you have a mega active, you get bonus candy and a chance at Candy XL every time you catch a Pokémon of a type your mega boosts.
My favorite active mega (technically Primal, but it works the same way) is Kyogre. Groudon and Rayquaza are also good choices, since together they give bonus candy across three different Pokémon types.
- Primal Kyogre: Water, Electric, Bug (types boosted in rainy weather)
- Primal Groudon: Fire, Grass, Ground (types boosted in sunny weather)
- Mega Rayquaza: Flying, Dragon, Psychic (types boosted in windy weather)
Mega level 3 (Max) usually gives 2 extra candy when the type matches, and XL candy about every third time on average.
So most mornings I search for "mega3" and mega evolve a Kyogre, Groudon, or Rayquaza that doesn't cost Mega Energy.
In this screenshot I have caught 59 Pokémon of boosted types:
