Public Defenders do not make the deal in your case, the Solicitor does. Your Public Defender only tells you what the Solicitor has offered you (and your PD tries to get a better deal). Your Public Defender does not schedule your case for court. The Solicitor does. Your Public Defender does not generate the evidence in your case. The Solicitor does.
If you have been arrested for a crime, the ONLY person who has your best interest in mind is your attorney, your Public Defender.