As I have experience with fentanyl I say fentanyl is better, you do not need anti-emetics, and it is easier to find, you can find it on the deep web, it is cheaper than nembutal and acts almost instantanious (you will be unconscious in seconds). If you buy it in the deep web buy a small amount the first time, just to see if it arrives. I did it and the product arrived in a letter envelope (more discreet than nembutal). 1 gram will do the job, as I have a friend who died of the same batch with less. Myself tried a little to see if works, and trust me, it works. This will be the way I CTB.