Are Orbital Sciences Corp's Mini-shuttles Viable Alternative

Dvice blog has an article describing Orbital Sciences Corporation's proposal to NASA's Commercial Crew Development (CCDev) program. OSC's project involves a lifting body concept much like NASA's Shuttle but barely a fourth of the size. This design is a dramatic departure from other purposed systems which lean heavily on the booster / capsule systems to deliver cargo and crew to the ISS.

From the Dvice article:

• ...the unnamed space plane has no engines like the shuttles, and it can only carry a crew of four. Like the shuttles, it would ride into orbit on a rocket stack - an enhanced Atlas V. It would dock with the ISS via a hatch in the rear, and after departing the ISS it would glide to a runway landing...

However the number one contender for the CCDev is Space X who has already demonstrated that their Dragon / Falcon 9 system is operational by launching and recovering the Dragon capsule intact. Space X ambitiously plans to dock with the ISS some time in 2011 putting it well ahead of the competition.