Celbi isnt a Counter, if you switch in while you think itll use CM it could may Sd or just be Physical with SD and then X-Scissor you. But even the Cmer could kill Celebi easily, if you use (and please dont laugh at me) Hp Bug. At first it may looks stupid, but It allow you to Ko Cele after one Cm. Lati@s, an other COunter for the CMer with HP-Elektro would be hurt hard too.
Of course then Gyara is a Counter, but it wount switch into Kerudio because it Exspect a Hp-Electric and get KOed and even if it would switch in, zhanks to SR-Weak and lack of recovery its much easier to kill Gyara as kill Latias or Celebi before Sweep.
So i think both could be used, so that the oppenent has to guess and then their will be no sure switch-in.
The better Move is of coure HP ELectric because Cele and Latias can be pursuited, but they arent that sure Counter as some People here may think ;)
Of course then Gyara is a Counter, but it wount switch into Kerudio because it Exspect a Hp-Electric and get KOed and even if it would switch in, zhanks to SR-Weak and lack of recovery its much easier to kill Gyara as kill Latias or Celebi before Sweep.
So i think both could be used, so that the oppenent has to guess and then their will be no sure switch-in.
The better Move is of coure HP ELectric because Cele and Latias can be pursuited, but they arent that sure Counter as some People here may think ;)