With one day, I would just purchase the single use EP and save the money. As PP mentions, the single use one allows you to use EP once per ride. The unlimited lets you use EP as many times as you want for each ride. With one day, there won't be a lot of time for re-riding anyhow. And if you can get there at opening, you can do several rides in the standby line with a low wait time and save the EP for a re-ride later in the day when the standby lines are longer.