The Army spent a good deal of money performing trade studies and simulations comparing an X2 configuration against both twin and quad tilt rotor configurations for their 20ton Joint Heavy Lift program. I believe the results of those studies suggested the twin tilt rotor configuration was best. However, the study requirements also may have been focused more towards speed, altitude and range, which would naturally favor a fixed wing airframe.
Full tilt ahead: What will follow the V-22?-07/11/2006-Washington DC-Flight International
Of course, the X2 was a more mature technology than either of the JHL tilt rotor candidates. And the X2 is currently in flight test (with private funding), while the QTR and OSTR concepts have not progressed much beyond powerpoint slides (paid for with $30 million of DoD money). So you've got to give Sikorsky's X2 group credit for that.