Living in another state while you go to college does not in and of itself change your state residency. While away at school, you are still considered to be living in your home state. So, for 2016, you were a Pennsylvania resident. If you are required to file, you will need to file a Pennsylvania resident tax return. If you worked in Delaware and are required to file there you will need to file a non-resident tax return. Your Delaware income will be reported as taxable income on both returns; however if you pay any state tax to Delaware, Pennsylvania will give you a credit for the Delaware state tax.
As for whether or not you should change your state of residence, you will have to weigh the costs and benefits of that and make the determination yourself based on the specifics of your situation.
