Pokemon DIamond:Who should I use?

Question

Heatran level 70 moves:

Scary Face

Lava Plume

Fire Spin

Iron Head

OR

Groudon level 78 moves:

Slash

Solar Beam

Eruption

Fire Blast

Who should I use?Thanks.

Answer 1

Heatran because it has more resistances and more immune then groudon. Just train heatran more.

Answer 2

Groudon because it's a higher level and it's attacks I think are better.

Answer 3

What are you wanting to battle?

...But I'd go Groudon, since you've had it longer, Heatran is a Just-caught Pokemon, right?