Thank you for your consult at DoctorSpring.com. My apologies for the delay, due to a technical issue, the consult wasn't received me till few hours back. However, I hope this reply and answer to any follow-up questions will be very helpful to you.
Yes 3D CT is a wonderful tool in assessment of hard tissue (bone) structures which are otherwise difficult to view in a 2D scan like a regular CT or an OPG (Panoramic xray). But the benefits are far more in your case because u need a bi-jaw surgery which is very difficult to plan in regular CT or normal xrays.
Just the chin or only lower jaw surgery i would not prefer a 3D CT, but bi-jaw associated with lower jaw assymetry i would definitely recommend its use.
Also the depth of bone to be cut, site of osteotomy (bone cut) and any anatomical variations can be clearly visualised in the 3D Ct, so please go ahead as is planned by the surgeon.
The only situation where i would suggest u to not opt for it is if u are worried about the costs involved.
Else please go for it. Time is not an issue here. It is worth the wait.
Hope this helps, please feel free to discuss further.
Orthodontist and Clear Aligner Specialist(Germany)