Misconception that public defenders are bad lawyers.

Hello all, why is there a misconception that public defenders are bad lawyers? I'm currently facing some legal trouble and people have told me I'm screwed because I'm using a public defender and have urged me to go into debt to get a paid lawyer. From what I understand public defenders are very experienced in their field and have alot of help, and also work with the prosecution to the point of knowing them and the ins and outs of the court. Am I really screwed having a public defender or are people just biased? I don't have alot of money and am not keen on going into debt if I have a possibility of getting my case dismissed.