In an out and out race, I believe I maybe faster on a 26 inch bike. I own a Ti 29er hardtail and really like it. I like it because I can ride it hard for an hour and feel less beat up than on an equivalent 26 inch hardtail. The difference in speed isn't enough to bother me either way.
No doubt a 29er doesn't accelerate as fast as a 26 inch bike. But keep in mind there is a reason that road bikes evolved to 700c wheels.
Once spooled up the big wheels really go.
I am not a snob in that I see room for all bikes. A lot of top racers have not made the conversion to a 29er for the simple reason that a 26 inch bike can be built lighter, it handles quicker and accelerates faster...admirable traits when out on the trail. I like to blast groomed trails without a lot of turns and for that a 29er is taylor made.