From what you've posted I take it that the 12 bit permits two separate feeds, whereas the 16 takes one feed. You might want two feeds if you have someone being interviewed. Both the interviewee and interviwer would be on separate stereo tracks (12 bit). The irony is that most theatrical films are actually shot in monorual and the tracks are splt, then panned to the correct location. Another reason is to create an out-of-phase track. I don't know how you'd do this with this type of equipment, but professionals sometimes will mic the atmosphere and have it out-of-phase with the actors mic. What happens is that the background sounds are eliminated. (One mixer told me how he used this trick when on location and shooting in an old barn that was home to pigeons in the rafters. He mic'ed the pigeons, put them out of phase, and viola' no pigoens on the track.) (A first had experience was while working on a dramatic series. The shot was of a guy that was thrown out of a third story window and landed on some trash cans. Stereo was relatively new to television at the time (80's) and the AP was told to check tracks. He listened to each track separately on a one head moviola and everything seemed okay until airing. What aired was the guy was thrown out of the third story window and silently landed on the trash cans--the FX were out of phase and canceled each other out.) Sorry about the OT stories.