Having ridden both, I much prefer the 29er hardtail. I do also agree that a 29er f/s is the way to go if money is not much of a concern.
The 29er simply climbs much better then the 26 inch counterparts, for me anyways.
What 26" full suspension is worse at all-mountain endurance racing than a 29er hardtail, based on your riding experience? I have time on HT and FS in both wheel sizes, and I can't believe anyone would pick HT.