Should I sing a high song for my audition or a low song?

I'm slowly becoming a high contender for many main roles in a very competitive theater company and have recieved roles with lines and one main role. The company is preforming suessical in the fall and I'm not sure whether to shoot for the high singing characters (gertrude and mayzie) or the lower ones (sour kangaroo, cat in the hat and mayzie). I am fairly confident in both my head and chest voice but I'm more confident in my chest. Help?