innerbeast should be used if your taking damage, or before an attack you know will hurt (revelation in t12, death sentence, things like this) unchained should be used when you want to do more damage, unchained + zerk + maim + bloodbath and OP spam is effectivly a regen aswell as holding hate on a group of enemies

while leveling, id say use unchained when its up and if its on cds use IB to help healers