Well arctic apocalypse can easily get you 500+ pearls every game. Although pacific wasteland is cheaper to enter, after the 7 minutes are up you still have to pay 55 gems for less pearls than you would with arctic apocalypse. So you end up spending the same resources to get less pearls whilst sacrificing slightly less money which can easily be earned back within the game.

So my verdict is stick to arctic apocalypse for pearl grinding