Good one. Awesome mechanic. The egg shape helps to make it pretty unique. A ball shape would be less random and control a little better. For a game jame, the egg is a good decision. For a longer game I'd go for the ball for sure. :D
I really think that the egg shape is what makes the game. With a ball it is much more predictable whereas with the egg shape you have think more about what you are doing and in what position the egg is in.