Depends on the situation mostly - each spirit does a different thing, and that skill can be applicable to PVE or PVP.
Usually, for me - I stick to using the Earth Spirit and Wind Spirit for PVP. Depends if I have the stigma Spirit Wall in, then if I do, I use the Fire Spirit. Earth Spirit is great for tanking - as well as the personal BG of the SM during PVP...Earth Spirit is interchangable between PVP and PVE. Water Spirit is practically useless in PVP, use it PVE for DPS. Same with the Fire Spirit. Wind Spirit is great for PVP because it can stun your opponent. ^.^ Earth Spirit is the t