no other way around, 2.8 is king (thats what i got out of it)
i am finding that i prefer the 27.5x2.8s over the 29x2.3s on my fuel, i havent gotten to do any playing on the stache yet to see how it compares to the 29x3.0 (yes i have a serious problem)
PRs on strava seem to support the preference too, but thats still only as clear as mud since there are some sections i have my PR on the 29r tires . . . (same tires in the two sizes so i can get a better feel for the effect of tire size) and even some on the 29+ tires on a completely different bike . . .
The narrowest, less knobby, largest diameter tire that will not pinch flat and have traction on rooty wet rock, while climbing, and descend while being in front of the group, with out a cut or flat gets my vote.
not really a scientific review, I'm sure @rick81721 could poke multiple holes in the analysis
If controlled studies matter to anyone look here: https://www.bicyclerollingresistance.com/
"Scientifically" Schwalbe Big One LiteSkins are the fastest tires out there for "dirt" 15.8w
Vittoria Corsa Speed for road 7.7w, Schwalbe Marathon Almotion for touring 17.1w and Schwalbe Jumbo Jims for fatties 36.9w.
@fidodie my personal experiment was to compare 29 and 27.5 based on my style of riding. Surprisingly I really preferred 29s is almost every place I rode, in 2.4. And found out the 29+ was a ridiculously fun tire size. To all tires their own...
i wish strava could sort your attempts by which bike you were using (per what you assigned for that activity) so i could look back at it that way, would make sense to have a 'false' bike which is the same with different tire sizes . . .