I really agree with garret94s idea as it helps you sort out and half-plan ahead of time what is going on. for example, If you are a horrible cardister, and you know that a cardistry contest is coming up, that gives you more time to focus on the magic/performance contest coming up.
I would really like to see a create your own card design, but getting it printed seems kinda like a pipe dream. Still I would love to see other peoples card designs.