My two cents....Photography does win, but just like a painting or digital work I think it has to be exceptional. A recent piece that comes to mind...Richard Holland from the Under the Sea exhibit. There were tons of pieces in that show. Richard's piece was exceptional, most of his work is.
If a photo is going to compete with paintings, digital works ect...the composition has to be strong. It really has to stand out, and as Muriel said a centered comp usually doesn't.
As far as a statement is concerned, I don't think it's always necessary to win but it does matter.
Popularity....probably, if I'm torn I do vote for the piece I'm more familiar with, which usually means I've seen their work more often. I think consistency is pretty important. I scroll before I vote and don't look at the names, but I'm betting that I could tell you who did the work very often without a name. That includes photos as well. Carolyn's piece deserved to win...it's exceptional, and like Richard Holland, her work is always good and consistent.
Wow, that's a lot of babbling....the fact is Bob asked the question.
Be who you are and say what you feel because those who mind don't matter and those who matter don't mind-Dr. Suess