You can totally make the Line Of Scrimmage argument because the Saints lead the league in drive success rate and yards/drive. So the Saints march further and don't get to the endzone vs GB marching shorter and getting more TDs.
Brees/Rodgers Relative Ratios (Brees as a % of Rodgers) [Difference in Rating]
Comp/Att: 70.7/68.2 (103%) [2.08]
Yds/Att: 8.17/9.2 (88.8%) [-4.3]
TD/Att: 0.065/0.089 (73%) [-8]
INT/Att: 0.02/0.011 (181.8%) [-3.75]
The largest deviation is in INTs, followed by TD/Att. Comp/Att caps at about 74%. Anything higher than 74 does not increase your rating. Yds/Att caps at about 11. TD/Att caps at about .11 INT/Att caps at 0. Every .01 is worth about 4.1 Passer Ratings. So looking at the differentials, despite Rodgers being nearly twice as efficient in INT/Att, it's TD/Att that really drives the gap between the two. Given the explanation I've put forward earlier, it's truly the most important of the stats we're looking at, and it's very exogenous to QB play. Of course we can look at the ways that Rodgers has edges, but in reality I doubt anyone would expect TD/Att to be such a decisive stat.
Remember that the median and mode here is going to be locked at 20 due to kickoff rules. Saints are literally last in the NFL in turnovers. There's about 150 drives for all three teams. I'm going to open excel here and pop down 20 for 100 cells. To get to 30, the remaining 50 drives would have to average starting at the 50 yard line. For 28~, where the Saints are, the remaining 50 drives would have to average starting at the 45 yard line line, 5 more yards per drive. That's 250 more yards over the course of the season that one team has to travel over the other. Also, realize that, on average, the saints start at the 28 and travel 41 yards to the 31 yard line. GB starts at the 30 and travels 39 yard, all the way to the....31 yard line! So the only explanations that describe the reality that is more TDs than the Saints is that the Saints are more consistent, whereas GB's variability leans towards a single tail. I.E. most of their starts are at the 20 but they get to start much closer to the endzone more frequently than the Saints get great field position.
Seriously the Saints started in field goal range like three times this season. One was the fourth down stop in Atlanta, one the Sproles kick return last week, and when they picked off Newton on the first play of the Carolina game. The total yardage difference, over the season, puts GB 300 yards closer to the endzone. If those 300 yards tend to come in large chunks rather than small ones (something there's certainly evidence for), they'll lead to more TDs. Oh and you can totally explain a lot of it with weird INTs like the one Brees had Monday where the endzone TD got popped in the air off a tip. Brady has a couple like that as well. Given the sample size, those anomalies can go a long way towards explaining why TDs drop while yards are so similar for all three. Again there is absolutely nothing here discounting the entirety of Rodgers. It's merely explaining the distortion that something exogenous can have on a passer rating.