d8 to d6 OR disadvantage

[Stegyre]

A math question!

Here's the difference, in a handy table:

Original Die	Original Avg.	Reduced Avg.	Disad. Avg.
d8	4.5	3.5	3.1875
d6	3.5	2.5	2.527778
d4	2.5	1.5?	1.875

"Original Die" is your starting die: d8, d6, or d4
"Original Avg." is the average of that die.
"Reduced Avg." is the average for the die one step smaller. (I've assumed d4 goes to d3.)
"Disad. Avg." is the average for the disadvantage mechanic with the original die size (the worst of two d8s in the d8 row, for example).

EDIT: As you can see, one method is not consistently better or worse than the other. Instead, the smaller the starting die, the worse a size reduction is, while the larger the die, the worse disadvantage is. This trend should continue. (I.e., if starting with d10, you'd much rather take a step reduction than disadvantage; if starting with d3, you'd much rather take disadvantage than a step reduction.)