Darkrai/Mewtwo/Terrakion or Bouffalant???

Heyy PC. I'm trying to run a Darkrai Mewtwo Bulls deck, but I don't know whether to run Terrakion or Bouffalant. Terrakion is a fighting type so it beats Eels and other Darkrai. Bouffalant has an edge against EX pokemon and has a built in Eviolite. What do you guys think?

Bouffalant or Terrakion?

I would probably lean towards Bouffalant because it fits in with the four DCE you'll be running. Not to mention to run Terrakion you would need to add in Fighting energy and Energy Switches which takes up more space.

If you wish to add in a 2nd attacker which is weak to fighting, making your fighting match up even worse...than go for it. You either keep in the 4 DCE because of Mewtwo or you drop your Mewtwo count, take out DCE and use Terrakion with fighting energy instead.
You can use prism energy instead, which allows you to run Shaymin EX and Keldeo EX which gives you counters against Terrakion and Landorus EX. However you will have to be careful of enemy "Enhanced Hammers".
Terrakion will give you the edge against enemy Darkrai EX and other decks which are prone to KOs through a good "Retaliate" such as an Eelektrik, Darkrai EX etc. Also just land crushing for 90 which is a OHKO against enemy Darkrai EX is pretty scary.