There are multiple ways and points you can use to communicate why CT coronary is preferable for your patients as compared to Traditional CAG.

1. CT CAG is non-invasive so minimal risk during the procedure
2. CT CAG is more accurate and especially with volumetric it gives you a deeper understanding of Plaque structure ( calcium capsule, lipid core, etc) thus understanding the real risk if any posed by it.
3. but the most important point of argument is the one you have mentioned in the question itself cardiologists prefer traditional angioplasty as they can use the situation to their benefit in convincing ( scaring) the patient and relative to go for immediate plasty. whereas in CT CAG patient gets time to evaluate the need for surgery. So I think this is also the strongest argument for us that we don’t need to that in CT CAG there are minimal chances of manipulation and push for Surgical intervention.
4. In cases where a patient who has agreed to your treatment the aim is to have a report which can be objective so as to be comparable pre and post. The traditional CAG which is reported subjectively by the performing cardiologist is not at all useful for the same.