I'd use the one that is shown in the first image. This is because of his sword side hand. The hand resting on the pommel of the sword indicades that he might not be in immediate danger.
Agree with izeColt. The extended arm overbalances the pose I feel. Great looking start to this character.
The first pic is better... More balanced, I think. And izeColt also got a point there! Also the first posing gives a feeling that something bad is about to happen, so it gives a better "story" to the mini, than just blasting with the bolter...
Vote for 1st image :D