The difference, by the numbers
Both have Angostura bitters. Only the Benton’s Old Fashioned has bourbon and maple syrup; only the Oaxaca Old Fashioned has tequila, mezcal and agave syrup. In parts, a Benton’s Old Fashioned is 8 whiskey and 1 maple syrup; an Oaxaca Old Fashioned is 3 tequila, 1 mezcal and ¼ agave. By volume, the Benton’s Old Fashioned is 89% spirit and 11% syrup and sugar; the Oaxaca Old Fashioned is 92% spirit and 8% syrup and sugar. That makes them close cousins on the ratio map.
The Benton’s Old Fashioned is the stronger drink in the glass (26.0% ABV against 24.7%) and holds more alcohol (1.56 standard drinks against 1.41). The Benton’s Old Fashioned has more calories (about 179 against 159) and more sugar (6.0 g against 4.6 g). Both are stirred and served in a rocks glass.