It is never a good idea to represent yourself in court if you are not a lawyer. It is an especially bad idea in a criminal trial because if you lose, you may end up losing your freedom for a long time.
People who represent themselves often make mistakes in court that work to their detriment. The prosecutor will be a lawyer with years of experience collecting evidence and presenting a case.
Defense lawyers keep up to date on changes to laws and the decisions of judges in various criminal cases. They will know more about what evidence is admissible than the average individual ever could.
A lawyer will also know what is admissible in court and what is not. They will have a staff devoted to researching your case, and they will have many legal resources at their disposal.