"the reason for the higher sensitivity over all compared with AUT. "

Stephan.. I would be very interested in reading the gentlemen's explanation in detail in regards to how how he figures CR is more sensitive than AUT. Especially for PAUT. (phased array automated UT)

There is a contingent of old school NDE types out there that are dead set on regaining RT dominance. However; that horse is out of the gate long ago never to return.
RT has come a very long way compared to old school methods, but it has some specific limitations.

I've had the good fortune to take part in some trials between phased array and CR. The result of which left me with a less than comfortable feeling in regards to RT.

Having said that, I see both staying around but RT in a limited role. The cost of doing both on a given project usually is the limiting factor, however; if you had a super critical
project, that would be your best method.

RT's primary limitation is in it's ability to pick up planar flaws. (cracks, lack of fusion)
UT's primary limitation is in it's ability to pick up volumous flaws. (slag, porosity, Tungsten inclusions etc)

Using porosity as an example for comparison: A pore will have a specific volume of missing material, this is an ideal flaw type for RT
Whereas a pore is typically at least a partial or wholey ominidirectional reflector in regards to UT. For UT the energy impinges on the pore and is reflected back to it's point of origin by only a small portion of the flaw as the rest is either refracted, diffracted, mode converted, or otherwise sent away from the receptor.
It should be noted that AUT can pick up on those otherwise lost waves and waveforms and be reasonably assessed due to using multiple channels/transducers/elements and the ability to tie those together in a coherent imaging process. (such as an Sectorial scan for PAUT, or phased array)

Using a planar defect such as a lack of fusion for comparison: This is the ideal flaw type for UT.
Where a planar is typically very tight in regards to it's width leaving a very small volume of actual missing material, which leaves very little change in material for the RT to pick up on. Even in that, the volume missing can be missed all together by RT depending on the flaw orientation, whereas UT, phased array in particular would be ideal to find this flaw type, as the angle of incidence can be dialed in and in the case of phased array, ranged in.

As for presentation, Old school UT was A scan (time distance trace), B scan was a side view cross section, and C scan was a top down view cross section. The current state of UT presentation is only limited by computer processing speed, which in todays world is several orders faster than when I began in the 80's.

Another factor involved would be the security and safety. This is the achilles heel of radiography. No matter what methods of presentations, accuracy, etc that you can come up with, it still requires a source of radiation. Unlike the world of yesterday when people weren't flying planes into buildings, today the risk benifit must be evaluated in regards to keeping these sources around. The more security the various nations of the world, the IAEA, and other authorities impose upon companies utilizing radiographic sources, the more expensive it will be to perform. Economics alone will start and has started in a lot of places, the move to something that does not require the sources.
I believe it will be this factor that ensures the dominance of UT as it can do all the above, but without the ionizing source.

Regards,
Gerald