I was also thinking of tax purposes. which state is better to
be a resident in.
You won't get to pick where you live for tax purposes. If you're working in California, you're paying California taxes. Otherwise everybody would maintain a P.O. Box in Tennessee or Nevada.
I kept my original license for several years until it was about to expire. I had a job in town and didn't have to own a car for a couple of years, so it wasn't an issue, but once I needed a car I didn't automatically switch it over. I had no problems buying or registering a car in CA using an out-of-state license, and although the subject came up at the DMV when I finally did get my license, the DMV didn't really care much less do anything.
The only way you're likely to hit a problem is if you're pulled over, but that never happened to me, so I don't know how much crap you could catch or whether being able to claim part-year residence as a student would avoid trouble.