The primary benefit is that you stay in the U.S. It is not automatic. If you are detained by the US, there is no guarantee that you will be released. You can’t receive a green card, petition for family or travel outside the US.
The main advantage of CAT protection is that none of the bars to asylum would prevent you from being granted this form of relief. Moreover, the torture you would face in your country of origin does not need to be on account of one of the asylums five protected grounds.You can also be removed to a safe third county, and your protection may be terminated if you are no longer at risk of torture in your country of origin.