I'm an attorney, though not a public defender. There's some accurate statements but also some information that isn't quite accurate.

The #1 reason has already been touched on. Public defenders have massive case loads. They don't have time to do complicated legal research on all those cases, or check through the ins and outs like a private criminal defense attorney will. They can't spend dozens of hours on a motion. They also have limited resources to hire experts, investigators, have associates read through thousands of pages of documents, etc. Private criminal attorneys have access to better resources and have more time to devote to the case.

Second, most of the people who became PD's are not PD's because they couldn't get a job doing something else. They are PD's because they want to (a) be a criminal defense attorney and (b) be in court. If you want to do criminal defense, there's no better place to get experience right away than at the PD's office. I live in a major metropolitan area. A lot of people at the PD's office went to some of the top law schools in the United States and could have gotten jobs at major law firms. They just wanted the chance to be in the court room and get experience right away.

Third, there is actually a high likelihood of getting a fairly incompetent attorney as a PD, but only if you're using one for a small-time crime. The reason is not because PD's are lesser lawyers, but because if you're using a PD for a low-level crime, you're going to get a kid who is very new to the practice of law. Any lawyer will tell you that going through law school and passing the bar does not make you a competent attorney. At all. It takes years to become competent. So if you're using a PD for like a misdemeanor or something, you're going to get a kid fresh out of law school. He's not incompetent because he's a bad lawyer, but because he's inexperienced. The more serious the crime, the more experienced the PD you're going to get. And the less likely they are to be incompetent.

Last, the federal public defender service has some of the top lawyers in the country working for it. If I got charged with a federal crime and I could choose between the federal PD office and an average private attorney, I'd choose the federal PD office each time. Most of the lawyers who work at those offices were some of the top law students in the country. At my local federal PD office, most everyone went to Harvard or Yale.