Board Thread:Questions and Answers/@comment-6011882-20130308145601/@comment-208.1.253.163-20130308214505

When you battle, all frontline cards of your element get a 5% bonus. And, since the best frontline cards are going to have skills related just to their element ("Great Boost" isn't always the same -- changing one specific parameter, like "Fire ATK," is strongest), it's best to load up on what you chose.

There's practically identical versions of each card across all three elements anyway.