Hi Gravity Predators: concept sketches

These are two concepts for predators on a high gravity planet for my children's picture book project, "Who Is Out There?".  Both creatures are designed to suggest common ancestry with two other creatures I've already designed for this particular planet.  I figured that the best way for a predator on a high gravity world to take down prey is to literally knock them down and let gravity do most of the work.  With that in mind I've created two ideas that could effectively accomplish this.  
The first one on top is a solitary hunter with head mandibles that work in a similar fashion to the forelimbs of peacock mantis shrimps.  The main differences is that the mandibles can move independently so to strike prey on either side of it's body.  The second one on the bottom is a back hunter that uses it's clawed forelimbs to anchor itself as it's swings it's spaded tail at the limbs of it's prey.  Additional torque is provided by a quick reflex muscle system connecting the upper and middle body.  I should add that bodies of both predators are covered in a thick-leathery hide that is light enough to allow pursuit of prey but strong enough to negate offense from said prey and competition.

Which Idea seems the most plausible?