In Hearthstone often I have the choice of attacking with a minion against a taunt, but it will cause a loss. The alternative, just leaving the minion on the board and doing nothing, risks losing it to AOE or a spell.
Above is a typical situation. I can attack the 2-6 Stegosaur with my Phoros. Then I might be able to kill it next turn by using the 3-6 Water Elemental and a Fire Blast. If I leave it on the board, I risk it getting killed by a multishot, but if he has no spell then it might be better to leave it.
Best Answer
Ask yourself this:
Conclusion: I would leave it up. If your opponent trades into it, you have the same result as if you attacked it. If he doesn't, you can attack it with your frost elemental over two turns and leave your pyros alive.