I can’t see how performance in wheel size as the OP suggests can be measured on anything other than road, as there are so many variables on the dirt. To say my mate is quicker on such a wheel size and slower on others, only proves that he prefers a certain type.
Masses of variables to make it in any way accurate to calculate. Faster in one way and slower in another is my opinion of all wheel sizes. Choose one that suits your riding preference, or multiples if you’re fortunate enough to afford them.
I ride 26 on the dirt, because I’m 5’8″ for a start, and more importantly perhaps, is that I love tight, super tight twisty single track. Gravity singeltrack and open descending yep, bigger wheels do seem more capable from what I’ve observed.