My entire family is from Mississippi, and I lived in Jackson until 6th grade when we moved over to Montgomery. Montgomery is, of course, right next to Auburn, but with all the politicians (i.e., lawyers) in town, there is also a tremendous support for Alabama. In addition, two Air Force bases are there, so you have a large number of transplants trying to remain neutral (my best friend was from Boston, and was an Oklahoma fan).
There are two main differences between the Mississippi Rivalry and the Alabama counterpart. The Alabama rivalry is bigger: The schools are bigger, the fan bases are bigger, the games are more important, and the rivalry bleeds into every aspect of life. But the Mississippi rivalry is MEANER. There is a level of hatred between the Mississippi schools that I believe is unmatched in college sports.
Growing up in Jackson, no one ever asked me which school I pulled for. My first day of 6th grade in Alabama, the new kid was asked at least 4 times if I was for Auburn or Alabama. I knew my family was Democrat (it was the 70's) and Methodist, but I didn't know where we fell on the great Auburn -Alabama debate. Several times over the years I tried to choose a side, but it never really took.
Unless you spend time in the state, I really don't think you can understand the enormity of rivalry. It is all-encompassing, and it never ends. It doesn't prevent people from forming friendships, business relationships, romantic interests, and the like, but its always kind of there...and in the Fall it gets intense. On the day of the Iron Bowl, there is a bit of a hush around the State, as everyone is gathered in front of TV sets to watch the game unfold.
Something they left out of the documentary was 1993....the year the Iron Bowl sold out TWO football stadiums. That year, Auburn was on probation and their games could not be televised. However, the NCAA allowed teams visiting Auburn to simulcast the game back to a location on their campus. Alabama chose to show the game on screens at Denny stadium, and sold it out.
OTOH, I never thought the rivalry in Alabama held the bitterness of the rivalry in Mississippi. There was always something just mean-spirited about the Bulldog-Rebel rivalry, that didn't exist so much in Alabama. We all told the same jokes, just substituting the names of the schools and mascots or whatever, but in Mississippi people really meant them.
My feeling about the two rivalries was echoed by a ranking in the Houston Chronicle back in the early 90s. The Chronicle ranked the Top 10 college football rivalries, by ranking several categories on a scale of 1 to 10. IMO, their ranking had too many categories related to the national rankings of the teams (categories such as national significance, quality of play, quality of players, etc.), and their #1 rivalry was Miami-FSU. Auburn-Alabama was either 2 or 3, and State-UMiss came in at #10.
The significant category to me was "hatried". State-UMiss got a 10. Auburn-Alabama got an 8. No other rivalry was above a 7. That seemed about right.