what is the major difference between high school and university when talking about accommodation?

Nothing is different actually.It is all up to you.In high school,you can stay home if you can walk to school in a few minutes.In college ,you can still walk to you college nearby.
Well,I think the major difference is that most people would like to go to university in another province.So it is hard to live outside as the fees are impressingly high .As a result ,you have to live in you dorm with your other classmates.
However,you can benefit a lot from it.Most possibly,you can find your true friends and build your relationship network,which is farely important for your futher!