From what's shown in the video, I would put some skinnier/lighter tires on the 29er and give it a go.

My stumpjumper 29er hardtail is set up like this. I have 1.95 Renegade tires on her at the moment and she flies on gravel and dirt roads. Pretty good on pavement too.

Of course as others have said gearing and amount of climbing could be the over riding factor on what bike to use.