Like the others said, Encore is superior, but I'm going to explain why. There are a lot or status or setup moves in VGC '16, and Encore is a terrific way of stopping Trick Room teams, Kangaskhan + Xerneas, Smeargle, Thundurus, and a host of other moves. Encore is so useful that it moves past the point of being a "troll" move and instead becomes a powerful disruptive tool. Here are some of the moves and strategies it can cripple:
- Xerneas' Geomancy. Lock it into this and you're free to take it out with Ferrothorn or Mawile.
- Fake Out users. Kangaskhan, Smeargle, Liepard, etc. do not like being locked into a useless move.
- Trick Room setters like Cresselia, Dialga and Palkia. Especially effective if they can't switch out, forcing them to instantly revert their Trick Room.
- Moonlight Cresselia on Groudon Sun teams, other recovery moves like Roost and Recover.
- Anything that has just used Protect.
- Any status move, like Tailwind or Rage Powder.
- Gravity teams.
- Quick Guard, Wide Guard.
- The odd setup move like Swords Dance or Calm Mind (although only the latter is really seen).