so here's why I like open mic's more:
1) Most of the performers are working comics or people who are trying to be working comics.
2) Open mics are an opportunity for them to try out new jokes, which means they often push boundaries - you see stuff that is more racist, crude, and "edgy", if you will, because they want to see how people react. This is often extra funny. When it's not....
3) people bomb. I like watching people bomb because it's a very real, human experience. If you're paying to see someone they'll generally play it safe.
Finally
4) you do get some really really bad people which isn't as bad as you think because it only takes like 5 minutes.