Can anyone explain challenge levels to me better than the game guide can? What s the reward of picking higher challenge levels?

As long as you are rehearsing enough, that means larger score gains towards the end of the season.

Right. Basically you set how hard your show will be. An easier show will give you a higher score up front because it will be easy.. but you will max out your show earlier and the harder shows will eventually pass you up.

They Basically nailed it. just try not to wait until it gets to 600 for rehearsing your groups.

It doesn't really matter when you rehearse as long as it isn't several hours after you have reached max energy... if you wait until it maxes, then you aren't missing out on rehearsal time if you rehearse the hour it maxes. so not waiting doesn't get you a higher score. You are just on more often to rehearse.