what are the disadvantages and advantages of participating in a competition?

Answer 1

The main advantages I can think of are:
* You get an idea of others levels of expertise.
* Right through life you will be faced with some form of competition, even job applications are a competition of sorts.
So practise is a good thing.
* Doing well in a competition can increase your self image.

I can only think of one disadvantage - losing!
But even that is an experience.

Answer 2

Advantages:
1) gaining credentials
2) networking with people of similar interest
3) finding out how you measure up
4) observing other people's "fast ball"
5) getting motivated to improve
6) having a focused moment of peak performance
7) adrenalin

Disadvantages:
1) temptation to hurt others in order to win
2) temptation to feel too proud if you win
3) temptation to feel too hurt if you don't win
4) temptation to ignore life for that one artificial moment