Posted 21 August 2014 - 13:39
There are numerous criteria, ranging from cargo capacity and safety to the business case - NASA wants a spacecraft with commercial viability so they aren't the only ones paying to keep it flying. The criteria are scored from red (bad) to green (good).
Commercial uses can range from flying missions for companies like crews & cargo to Bigelow Aerospace commercial space stations to flying missions for other countries or the US military.
In the last business case evaluation Dragon V2 was green and both CST-100 and Dream Chaser yellow.
Since then SNC's Dream Chaser is being looked at by both ESA and JAXA (Japan) to fly missions for them. DC is also relatively inexpensive to build and operate. This offsets the cost of its primary Atlas V HR launcher.
Boeing's CST-100is having trouble making the business case because of both design choices that drove up costs, one being an expensive Apollo-like disposable service module and another the high cost of it's primary Atlas V HR launcher.
Dream Chasers main advantages over the capsules are It has a very low G re-entry at just 1.5 G, a wide cross-range (can land 1,500 km to either side of its orbital track - basically any major airport) and its propellants are "green," nitrous oxide and propane. The low-G entry would be useful for medevac and sensitive experiments.