HTR pros and cons:
I'm strictly a mechanical systems guy with very limited knowledge of rotorcraft aero or dynamic issues, but here's my two cents:
In short, the HTR seems to be Bell's attempt to circumvent Sikorsky's X2 concept. Although it's hard to tell from the images, it appears as though the HTR's rotors might actually intermesh slightly. A large diameter rotor that doesn't fully tilt (like the V22) would seem to help make the HTR more efficient than a conventional tilt-rotor, without the need for a multi-speed transmission like the X2. Even though it would have a lower forward speed, apparently Bell thinks it is a better compromise overall?