Advantages of Entering Competitions
Game design competitions can be helpful in many ways, especially for the hobby designer (i.e. one that does not work for a publisher or does not depend on game design income).
First, it usually provides clear boundaries as to game materials and other factors, such as target group and even theme. These outside limits help a designer immediately focus. I've written before about the need of self-imposed limits, when one is designing on spec rather than on a contract basis. A competition usually has many of these limits built-in.