It usually depends on the frat, school or nature of the party. I wasn't in a frat but was friends with a few guys who were. The ones open to all tend to be annoying - tons of underage kids, cheap beer and a lot of standing in a loud, crowded, usually way too warm house. Other parties that were on an invite basis were better - better beer, someone manning the grill, beerpong, elbow room. After I turned 21 I dropped the open party, freshman bar scene like a bad habit. Wings, good beer, darts and a place to sit down (and like minded girls) = a way better time than a 5$ solo cup of beast.

A lot of irresponsible drinking, too often done by underage children who can't deal with reality.