Vote! Do you prefer to go first or second? Going second means you get the coin, and get an extra card to choose from.
If I go first, I generally find myself on the early offensive. Always more fun that way.
Do you use a lot of 1 mana cards?
I prefer 2nd, but I don't really mind going first.
I think having the decision to use the mana coin can mess up your play sometimes, or may not even be used at all.
Depends I believe for mage miracle rogue and druid it's good to go second.
Because for druid you can coin out a wild growth on second turn
Mage you can get a fireball off antonidas
Miracle rogue use it to draw an extra card with all those preparation and all
Also probably in handlock deck to get mountain giant earlier or a stronger twilight drake

