[@balthazar007] I think me and [@eklispe] came to the conclusion that the person who attacks first in battle generally wins since there's no mechanism about how the hit actually works. You stated that it's not wise to put in all of a Pokemon's EP into the first move, but doing so would force the other trainer to expend equal EP and therefore be left with less EP for their own attack. Because of this, the challenger/first attacker basically always wins.

Eklispe, confirm?