Congratulations to Rocketplane Kistler and SpaceX for obtaining the COTS funding. Speculating on what made them stand out made me tentatively conclude that the reason is because they are better financed or have more developed products than their competitors. I had almost expected that Spacedev would be one of the funding recipients given that they are the only company offering basically a spaceplane. Nasa's approach makes sense however. It's a survival of the fittest principle borrowed from nature, where the mother favors the stronger young over the weak at feeding time!
Continuing with this analogy, in the future if either SpaceX or R.K. appear to be not delivering the goods, funding should be diverted to another contender to ensure the best solution is given the best chance of survival.