Welcome to the Devil's Advocate.
Each week I'll look at an issue from both sides, arguing both ends against the middle.
The Houston Texans clearly have the best defense in the division.
The 2011 Texans dominated the NFL defensively, ranking second in total defense, second in NY/A, third in yards per play, fifth in sack rate, and fourth in points allowed. For a defense, points allowed is really the only thing that matters.
Under Wade Phillips, the Texans dominated, and came up especially large in the playoffs. The defense allowed just 30 points in two games, but 14 of those came on very short fields thanks to Houston turnovers.
Just within the AFC South, the Texans dominated. The south averaged less than 14 points a game against Houston. The defense was so good that not even the loss of Mario Williams was enough to slow it down.
2011 is over though, and the Texans have lost some defensive talent. It's not nearly enough to flip the rankings, however.
Williams was a great player, but the Texans played better without him.
Most importantly, the Texans don't have a single significant player older than 30 years old at the start of the season. The Texans also have six key starters who are 25 years of age or younger.
This defense already played at a championship level in 2011, and will only get better from here. They are not only the best defense in the South, but the best single unit from any team in the division.