Like it or not, you are going to have some lousy performances in dance. I just did a well rehearsed Samba in competition and did a lousy performance by making some stupid mistakes. Don't worry about a bad performance. You have a better chance of doing well with a showcase since it's only one dance.
In competition one does multiple dances--I did 15 different dances in my last comp.--made some mistakes too--so what.

You probably should do the showcase to just you past your fear of mistakes or a bad performance.