I was in your exact position for a while! If you want to do criminal law, you should probably do prosecution, because it sounds like you wouldn't be a good fit for defense, especially a PD office. From the PDs I've talked to, you need to be able to separate the defense of your client with the defense of the crime in general. You have to believe that every person deserves a defense, and that your role is vital in ensuring your client's right to a fair trial.

Why don't you try working for a DAs office while in school and see if you like it? In general, if putting people who deserve it in jail is satisfying to you, then it sounds like it's a fit. But don't also expect to have a ton of power to say no when you have to prosecute someone who doesn't deserve really it. As someone who works with low-income young adults of color, it happens quite frequently. I've heard many iterations of the backpack story with different details. How often this would happen to you would depend on your local office. There are more and more progressive DAs out there, I am sure there are no shortage of them in California. Do your research so you can get the best of both worlds.