Answer? Arkansas 2012 was terrible.
Seriously, the differences are more contained than you might imagine.
First, Brandon Allen. Arkansas scored 13 fewer points per game in 2012 than in 2011, but Tyler Wilson, when playing, was virtually the same guy. He completed 63% of his passes in 2011, 62% in 2012. He averaged 8.3 yards on completions in 2011, 8.4 in 2012. He took a step back in the interception department, and his EPA fell from 108 to 70. Adjusting per play, Wilson was about 2.3 points per game better in 2011 than 2012. When you consider the receiving options Arkansas was rolling out for some games, Wilson's 2012 numbers are not bad at all. Brandon Allen, on the other hand, was on the very short list for worst quarterback in college football in 2012. I recognize that he did throw 18 of his 49 passes against Alabama, but he was even worse against La-Monroe on 20 throws. Arkansas would have been 29 points better in 2012 had Wilson attempted Allen's 49 passes, and that number grows to about 40 points if we consider Wilson's value in maintaining drives.
Second, turnovers. Arkansas was +1 on turnovers in 2011. In 2012, they were -19. Net, they were -55 points from turnovers (4.5 points per game; just under 5 points per game versus 2011). The INT margin alone went from +5 to -10. Half of this was that Wilson doubled his interceptions and Brandon Allen was almost as good at targeting the wrong colored jersey as he was his own, but the Arkansas defense failed to get their hands on passes as well. Then there was Knile Davis. Davis was more likely to drop then ball than any non-quarterback with at least 100 touches in the country; lucky for him, Arkansas recovered most of those fumbles. But, in a vacuum, I would propose that Arkansas would have improved its yards per carry if Mr. Butterfingers could get a grip.
Finally, pass defense. Arkansas was significantly better against the run in 2012 than in 2011. And if you throw out Alabama and A&M, who averaged 5.0 and 6.8 yards per carry against the Hogs, the run defense was stellar. That would have been more important if teams had needed to run the ball. That was not the case. Teams improved their completion percentage against Arkansas by five percentage points, but more important, the yards per completion jumped from under 11 to 13.3.
In short, Arkansas 2011 would beat Arkansas 2012 by about three TDs on average. I would argue that more than two-thirds of that gap was a product of 1) Tyler Wilson getting knocked out of a couple of games, 2) the Arkansas secondary playing like Texas 2012 v. Oklahoma and 3) ball security issues for Wilson and Davis.
The Statistical Review breaks down teams along a number of performance categories, everything from red zone scoring to field goal percentage, and compares that performance against the rest of the FBS. All 124 teams will be reviewed from 124 to 1 by the hybrid rankings. You can find short descriptions of the stats used in the table below.