Legend has it that the mine howls out the last words of those who died inside
Garruk is a little safer to flop onto the board, comes out sooner and easier and kills a little quicker than Bolas
This, like future color fixing above, should be a super slim tiebreaker when trying to make the decision
For example, if Thrasta and a 2/2 Bear Cub are attacking a planeswalker with seven loyalty counters on it (and are unblocked), Thrasta can assign 5 damage to the defending planeswalker and 2 damage to the defending player
Its cheap, the ability costs nothing, you have no timing restrictions, and you can even eat Treasure and random artifacts like Mycosynth Wellspring for extra value
Rockets Mewtwo demands a high price (via TCGplayer) due to its Team Rocket association and release after the first Pokmon movie