After playing all 4 of the developer challenge's entries here are some considerations:
Entry #1 (Ando): The ability to reverse-thrust is a great feature. This gives the user increased precision in controlling the direction and speed of the ship.
Entry #2 (badkneecap): I really like the neon-like glowing graphics effect.
Entry #3 (Phaelax): the graphics are superb, especially the rotating rocks and the debris/fragments in the explosions. I also like the gameplay mechanics of the colliding rocks that rebound and change direction.
Entry #4 (VN): I really like the well-placed audio, each appropriate for specific game events. I also like the innovative design of mining the fading remnants of destroyed rocks for extra points, and the online (or local) high score table.
After giving it some more thought and reflection, I am submitting my vote for entry #3 (Phaelax's version).
I love that instant laser beam! And the way the rocks glow red when they absorb a hit, and the way that they collide and rotate. I also like the visual effect of the flying debris when either a rock or the ship gets hit. And the small graphical details like the ambient light on the ship when the laser shoots. I like the mechanical feature of the rocks colliding and changing direction. That adds a unique spin (no pun intended) / feature to the game.
I enjoyed playing each one of the entries. It would be neat to see (and participate in) more of these challenges in the future. Thanks for submitting the entries, each one was fun to test and review!