Quick sylveon question

[Smayjay14]

Should I run shadow ball or psyshock on my sylveon? It's info is:
Ability:pixilate
Modest nature
Evs: 252 sp.attack, 129 hp, 129 speed
-hyper voice
-wish
-heal bell
-psyshock/shadow ball

 

[Magcargo]

Please use the SQSA thread next time instead of making a thread for these types of questions.