Psi.
Telekinesis for the win right?
World of Jackcraft.
Depends of the defender.
Overall, my first pick would be power for pve and psi for pvp.
Ive always gone for psi, even pre pvp, the hold, the psi resistance, the ability to backup tank certain psi av's while the poor invince tank crys on the ground.
Power always tempted me but the hold from psi won me over.
Electric was once worth a look the end drain was noticable, alas no longer.
Dark, what can i say, if i wanted a power that killed me faster I'd have taken absorb pain.
So pvp combat psi, the ranged hold has no contest.
Pvp empath, i assume thats what your after 
power then is worth a look, last I checked buildup also "builtup" your heal and other aspects of your castable buffs.
what do people view as the best ancillary pool for 1) PvE and 2) PvP?