I went for a ride around a local field this morning. 6 miles, mostly flat.
My time on my 29er Singular Swift (just under 27 minutes) was within 15 seconds of my time about a month ago on my 26er Inbred.
The grass was shorter back then, and I was younger.
So, do 29ers go faster or not? Or is more data needed? Or gears? It certainly *feels* faster.