In terms of points per game allowed and yards per game allowed, Alabama has the upper hand here, even when accounting for the level of average offensive play in a given season. In terms of individual stat categories, it's clear that Alabama dominated, collecting more tackles, TFLs, fumble recoveries, sacks, interceptions (by a whopping 30), pass deflections, safeties, and touchdowns. In fact, the only category where Oregon bested the Tide was in forced fumbles, where they edged Alabama out 5-4.
I took the % of total stats that each team had relative to the total of that stat accumulated by all teams in the given season to come up with "Stat Share." From there I divided that number by the league average of 12.5% to come up with a number that represented about how much better that team was compared to league average, which is the "Over/Under league average" row. The sum of that row, from tackles to TDs is taken and divided by the number of stat categories looked at to come up with an average of about how much better the defense was compared to an average defense in the season of competition.
Both in raw terms and in relative terms, Bama is clearly the gold standard here still. So remember kids, if you think your defense is great, then be proud of them. But they'll never be what S9 Bama was.
Data linked below, sorry but Excel formulas don't transfer well to Google Sheets.
S11 Oregon/S9 Bama