Jimmy M. said:
Since both the cue ball and the object ball are the same distance from the rail, you're really not dead straight in. To be dead straight in, the cue ball would be slighter further from the rail than the object ball.
This is correct, but keep in mind that the greater the distance is between the cueball and the 8-ball, the less angle there will be, and the less distance between the balls and the side cushion the less angle there will be. The corner pocket gets smaller the closer the balls are to the side cushion. For example, in this case with the distance between the balls and the distance from the 8 to the pocket, if the cueball and the 8-ball were both nearly frozen to the side cushion, I'd consider this a straight-in shot for all practical purposes.
The example is underdescribed, because we don't really know what 'medium-tight' pockets means, or more to the point, how much we can cheat the pocket with speed and still make the 8. 'Medium-tight' should refer to more than just pocket size, but how the pocket accepts the ball on different shots, which is not quite the same thing.
It gets down to rough percentages. Suppose I'm 95% to make the 8 on the firm shot taking the cross-side bank, and 75% to make the bank from there. That makes me ~71% to get out. Now, suppose I'm 85% to make the 8 with draw for a cut on the 9, which I'll then make 85% of the time. I'm ~72% to get out that way.
Another caveat--I'm much more likely to sell out if I miss the cut in the corner, I believe, than if I miss the cross-side bank.