Playing the course lets me know how my drivers, irons, and short game is working. Now that I know what my clubs are telling me, I will be able to take it to tomorrow's game.
As Phil Blackmar talked about, the mental game is everything. If you are concerned about your opponents, you might as well go home.
Here, I'm using a couple of wedges to practice with. Knowing what shots you are going to use before they happen gives you a massive advantage in play.
Knowing the pace of your greens is one of the best things you can do to practice for a tournament. This will arm you with an advantage for not just putting, but chipping as well.