Court-appointed attorneys have huge caseloads, and a fixed government salary. In short, they are not motivated to work your case - there is no financial incentive for them to win or lose your case. Their primary goal is to spend the least amount of time on your case - which means they will usually pressure you to plea-bargain your case even if you are innocent.
Hired attorneys have a financial interest in a positive outcome for you. Their reputation is at stake.