Espeon

Use the C/PB as a defender.
No need to power up. When you come across a gym that he can get a middle spot, use him.

ZH/P is the worst moveset both on defense and offense.

is like alakazam in attacker, hits hard but has low stamina and defense, so have to dodge with him and has more cp than alakazam

I don't think that what happens on paper is always what happens in life.
they're both high enough and equal level that you can just use them and see how they feel and let us know your experience
attacking into psybeam can be painful so i'd at least keep that one for defense.