On balance, I think my 29er is slower than my 26er but makes me faster. Make of that what you will 😉
It’s all individual. Matt’s test gives the results for Matt. If I did the same test with my skills, the results might well be very different!
And there are many other variables (geometry, tyres, weight, forks etc) that can have just as big an impact on speed as wheel size.
But ultimately nobody’s making 26″ XC race bikes these days so the decision isn’t really ours any more.