To start I'm 6' 345#. I know there is a huge difference between the two, but what is it? I demoed a Niner Air 9 RDO a couple weeks ago and LOVED it. It climbed so much better than my AL 26er. I'm sure a lot had to do with it being a 29er, but it probably weighed about 2-2.5 lbs less. I'm trying to decide between a Cannondale F29 AL, Niner Sir 9 and an Air 9 RDO, they Air 9 being the most expensive for obvious reasons. I talked to the Niner rep and he said there is no weight restrictions on the RDO so warranty won't be a problem should I crack it. Will there be enough of a difference between the frame materials that I would notice a difference? I ride mainly road and light XC with lots of roots and rocks.

The components are the same on the SIR 9 and Air 9, SLX, and X9 components on the Cannondale.