Please, no "I feel like _______"; I understand the things to theoretically weight against one another but would love to see some hard proof either way!
Unfortunately its going to be very hard to get any reasonable data to back up either claim as there are so many variables to consider that its virtually impossible for it not to come down to a "on the trail it feels like _______" type statement.
Besides one person thrashing two comparative bikes around the same loop and comparing times (a 'test' which is so fraught with potential problems that it could hardly be considered as a reasonable scientific comparison by any measure you'd care to name) what data would you like to see exactly?
The 26er dually vs hardtail debate has been around longer than the 26 vs 29er one and to my knowledge there is still no hard data to support the claim that either is significantly faster than the other such as to warrant one not being developed by bike manufacturers any more.
How about the fact that the actual difference between the angle of attack of a 29er vs a 26er is only barely within the realms of what is able to be detected by human perception (~5% IIRC)?
Or that the shape of the tyre means that the contact patch will be slightly longer but in order to maintain the same size, slightly narrower too. This means that it will be better in longitudinal directions (whent the bike is upright) but not quite as good laterally (cornering)?
Ride both, decide which is best and then enjoy the crap out of it I reckon!