They currently convert 76.5% of their 4th downs, compared to a league median of 50%. Regressing them to the median would result in 4.5 more failed attempts. They average 2.54 points per drive, so 4.5*2.54 = 11.43 points on the season, or roughly 1 point per game. According to Vegas, a 1 point shift in point spread averages out to a 1.3% increase in win probability.

So about 1.3% of an advantage.

To counter this: in their last 8 MNF games the Vikings are 3-0 against the Bears and 1-4 against all other teams

Bears haven’t beaten the Vikings since December 2020 (1070 days)