Surprised not to see this already posted -
You base your choice on where the opponent's balls are lying. If balls from their group are still on the table, and near the upper corner, you cut with the idea of hanging the 8 if you miss and blocking their ball. If their balls are near the lower corner, you bank softly with the same goal. Any time you're taking a missable shot you have to be playing defense in some way. Of course, if it's like a 90% shot for you, you might be better off just cinching it.
If you're both on the 8 ball, you bank it even though a cut might be a little easier to sink. Except this time you hit the bank with speed, hoping to the 8 flies away from the pocket if you miss. Depending on the angle I might even hit hard enough to try to spin the cue ball up to the head rail and leave it stuck there. When it's almost straight in though, that's a tall order, and you don't want to Z bank into the wrong corner.
Another option, some feel more comfortable making thin cuts with inside. You can basically play to overcut a little with inside, with the idea being that if you do overcut, the cue ball zigzags to the footrail while the 8 ball banks off the foot rail and comes back up. Then the opponent is stuck with their own bank. If you miss the 8 entirely you'll still kick it from behind. But then it's up to lady luck if you sell out or not.