Choose. (Half of the top-rated speed)
My best guess for overall quality, based on various pieces of information posted on this site (I don't have a drive that is a good scanner).
On the subject of 16x burning I've yet to see it in Prassi ONES it seems to override my setting and drop to 12x.
The Prassi Ones has two different readouts for speed - if you double-click right about the speed, it changes it from averaged speed to current speed.
Ones gives me choices that are all the speeds available in the firmware, plus MAX, MED and MIN. If you are selecting MAX and get 12x, then perhaps the firmware does not have a 16x choice for that disk (ie for that MID code).