Considerably less invasive - no catheter threaded in to the blood vessel, probably less radiation exposure.
I haven't had the procedure done, but have had a few CT scans. You have an IV line, they inject contrast medium into the line and do the scan - it's simple.
As the contrast spreads, it tingles, and you get a sensation of heat - I didn't find it unpleasant, but some people do.
The contrast medium can cause a strange taste in your mouth.
If you are allergic to iodine or to shellfish, they either have to use another imaging technique that doesn't involve contrast medium, or they have to give you a prednisone blast to suppress your allergic response.
