[@Thundercrash] yeah, since Groudon is a ground type and creator of lands she should have generally more destruction skills, while Heatran is much more specialized in vulcanos and is a fire/steel type, meaning he should be more focused on lava and durability. Besides, Heatran is a sp. attacker with good defense and sp. defense, and Groudon is mostly focused on attack and defense.

TL;DR: [@Thundercrash] is right :P