I don't think Stephanie is annoying at all. I enjoy her enthusiasm, but then again, everyone holds different opinions.
A big reason that has to do with the OCMs acting the same is less air time. Much more of TWC's coverage is pre-recorded footage of weather news, and actual weather segments appear to be cut shorter because of this.
Ray Stagich does a good job at distinguishing himself from other OCMs. I've always thought that way about him.