Beck and Hannity are scrapping for the same audience, white women who want to feel good about themselves, so of course there is a bit of rivalry. Beck is winning that contest, Sean still leading with lonely Long Island houswives though.
There is no reason people can’t listen to both. They have separate time slots. At one time, I found Hannity to be more educational and Beck to be more entertaining. But now, I’d have to say that has reversed or, at least, Beck has become more serious and educational lately.