On a Diamond table, bottom right because the full pocket is open. It is typically considered the correct shot. But if you are playing on a Valley bar box, or a big table with loose pockets, or even a Diamond with brand new cloth, and you are doubting yourself, feeling so nervous that you can't shake it, it might be better to slow roll the back cut. I mean, on a loose table or on new cloth that slides a lot, you could hit the 9 way off, sending it an inch or so above the pocket into the side rail, and still make it because the pocket will play much wider at that angle. It all depends on your level of confidence at the moment.