The following is backtesting of NFL data for the 2014-2021 seasons in which the Spread is bet on the favorite team if the difference between the spread and moneyline probabilities of the favorite team winning is between the thresholds, and the Moneyline on the Underdog is bet if the difference between the moneyline and spread probabilities of the underdog winning is between the thresholds.
| Years | SpF | MLU | SpF | MLU | SpF | MLU | SpF | MLU | SpF | MLU |
|---|---|---|---|---|---|---|---|---|---|---|
| 2021 | -1520 | 450 | -1960 | 750 | -2430 | 1045 | -1860 | 1245 | -1180 | 225 |
| 2020 | 220 | 285 | 130 | 285 | -1020 | -1535 | -770 | -1510 | 280 | 490 |
| 2019 | -2020 | 35 | -1970 | 335 | -2880 | 445 | -2560 | 395 | -470 | -575 |
| 2018 | -470 | 25 | -460 | 25 | -1350 | -50 | -1320 | -140 | -110 | 90 |
| 2017 | 270 | 370 | 180 | 370 | 120 | -130 | 230 | -30 | -50 | 220 |
| 2016 | -1030 | 581 | -790 | 504 | -1640 | -517 | -1160 | -287 | -840 | 347 |
| Sum | -3030 | 1296 | -2910 | 1519 | -6770 | -1787 | -5580 | -1572 | -1190 | 572 |
| 2015 | -720 | -1105 | -870 | -1105 | -1530 | -1006 | -1830 | -446 | -340 | -770 |
| 2014 | -420 | -720 | -420 | -720 | -490 | -295 | -560 | -295 | 10 | -300 |
| Sum | -5690 | -79 | -6160 | 444 | -11220 | -2043 | -9830 | -1068 | -2700 | -273 |
Note in this table that the Moneyline bet did very well, except the years 2014 and 2015. For this reason, I additionally added a sum of the winnings after the 2016 season. I hypothesize that this is due to the prevalence of sports betting in more recent years, giving the spread probabilites a greater chance to move due to the voice of the masses.
It appears that the Moneyline is sensitive to the lower threshold of the difference, but not so much the upper threshold of the difference. This is especially true in the year 2020, where a lower threshold from 0.08 to .01 makes a huge difference in winnings/losses. This is also observed in the years 2014-2017.
The Spread bet is never good for any of the years, reaffirming the thought that the spread is more reflective version of a teams probability of winning by the masses. As such, it better to bet the Moneyline on the Underdog that the Spread on the Favorite when there is a discrepancy.