Personally I experienced both, I lived briefly in a dorm with 50 students abroad (sydney AU) and that was a whole lot of fun. Get used to it because it's never quite..... never.... and you can't be a party pooper because you have to go go go and you'll meet allot of people fast!!! So if your a social person or someone who has trouble meeting new people, a dorm is a great way to get integrated into the community.(get into study clubs ect) The big con is the privacy and quite time issues.. it's just more difficult to have some real time for yourself or feel fully at home.
So on the other hand I now have my own (clean) apartment and it's totally mine and a custom fit to how I want it and gives me allot of quite time for studying. Plus it's a bit more independent and you really learn to take care of yourself. (Also if your dating it's a big plus LOL)
In the end I live together with my boyfriend because it's cost-efficient and gives us triple the space to live instead of in a dorm and gives us a lot less hassle to be together when where not studying.....
BUT: If I did not have a boyfriend I would rather stay at a dorm close to my school, I realize by putting myself outside of the direct surroundings of my school I sometimes miss the direct connection with other student and don't always get the full student experience what I sometimes kinda miss but luckily had my fare share of during my year abroad what I wouldn't trade for anything!