As one of the people in costume for this event (The GCPD officer, actually), I gotta say that the contest side of the event was a bit skewered in its selection process. There wasn't much of a 'Entry Form' frankly, the sort of just plucked you out of the crowd if you were standing near enough. As for the Adults going up against the Kids, well... its an all-ages event, and when they throw everyone into the same category, its gonna get messed up real quick.
Perfect example is how on the second-last day of the event, a Lego Batman showed up in the last five minutes of the day as everyone was lining up for the competition selections, and took home $1000 for being in the park for five damn minutes, when plenty of others had been in-park, working the crowds all day.
I'm honestly hoping that the next event has a bit more organisation in this regard.
As for the guy who took home the first night's prize as the Arkham Knight, I know him personally also- really nice guy, and completely surprised they picked him- honestly we all were expecting them to go for the kids over us, we were just there for fun and photos. But hey, it happens...
Regarding my GCPD uniform though, I assure you, I do have more costumes than just that one- though it is my flagship costume that I am most proud of for it's screen accuracy to The Dark Knight movie, hence I wear it quite often. As for wearing it for the majority of the event, that mainly falls to the fact that it is currently the only DC themed costume I own (thats due to change soon, gonna throw together Rick Flagg).
I don't have many costumes, but the ones I have I make sure they're done damn well, and I take pride in all of them.