Fun article by my old pal and racing nemesis Steve Z about 26″ vs 29″ wheels.
Steve found what I generally have, which is that if you’re concerned with nothing but speed, it’s pretty much a wash (at least if you’re comparing bikes that are roughly equal in fanciness, which in this case he really wasn’t, but whatever). The motor matters more than the bike – if you’ve got the legs and the lungs to make the podium, the bike choice doesn’t matter much, and likewise if you don’t have those legs/lungs, a 29er (or 26er) won’t suddenly make you into JHK.
Then again, most of the folks I build bikes for don’t race in any serious way, so the most fun bike is the best bike, for them. If your paycheck comes from an actual job, rather than race winnings, you might like the big wheels a lot better. I know I do, because I can clean more stuff uphill, don’t have to use as much (or any) complicated and failure-prone suspension parts, feel like I get better traction, etc, etc.
Now let’s all email Steve and complain about how the test wasn’t fair. Every half an hour. For 3 weeks.