As a former actor, I understand the trials of marketing oneself (and accept them, begrudgingly). Many of the things we do in life are contests of a sort. Job interviews are a competition against others to see who will win the prize of being hired. Auditions are job interviews in which the actor often competes publicly against his/her fellow job seekers. Writers submit queries or pitch their work to agents to hopefully join the ranks of the published.
Gaining access to the agents is a sometimes difficult and costly thing (at conferences, for example). But contests can sometimes help get your work noticed. Are they worth doing? Of course they are.
I just finished (a couple of weeks ago) participating in a a contest called the 3-Day Novel Contest. It’s similar to NaNoWriMo, except the contestants have only three days to write a much shorter novel than is suggested for NaNo. Or more likely, a very long short story, or very short novella, take your pick.
At the end of three days, I was exhausted, but had a (reasonably) fully-formed novelette that actually was coherent. A miracle. If, out of the other 300 or so contestants, I happened to win the contest (another miracle), my novel would be published. A prize worth having, obviously. The winner will be announced sometime early next year, and I will edit and polish it some more while I wait.
However, having an agent look at some of my other writing in the meantime would be a good thing. I have one finished novel, If a Butterfly, which (I have stated elsewhere) is way too long for most agents to consider, so it might soon take a back burner to my second novel, The Jagged Man, which needs some more rehearsing before it can go on the stage.
You should check it out.