Thanks for clarifying that.  There is something wrong there. Or maybe not. Do you know what hydraulic system was used in those tests?

With all the row unit mounted airbag planter attachments shown at Louisville this year I am very concerned that folks lose sight of the fact that every time unit mounted air row cleaners or air closing wheels are either manually or automatically adjusted, that changes the down force on the vee opener and gage wheels. 

Even with auto row unit down pressure the row unit reacts trying to compensated but generally not quickly enough in some systems and the whole system just hunts back and forth, getting unstable. Meanwhile the planter at 4 or 5 mph has moved to a different soil condition and the process continues...same thing if you change forward speeds, the whole system becomes unstable.

We have seen very large differences in the row cleaner down force required to do a good job as a planter moves across a field with our very successful, frame mounted Gfx row cleaner. Putting this variation in down force into the row unit rather than into the toolbar creates a very difficult situation for the row unit down pressure system. Add closing wheel down force adjustment and you can imagine what happens.

The row unit down force needs to be a very quick acting, low resistance, system. Add in hitting a rock at 5 mph and if the row unit system has significant resistance or hysteresis it is likely something is going to break on the row unit.

If I take the "data" offered above to be correct, there is something wrong in that system used for the tests which is causing seed depth variations and/or closing differences between the airbags and hydraulic systems.  As other have posted in this thread, a properly designed and operated hydraulic down pressure system (most likely without unit mounted air row cleaners or closing wheels) leads to visually more uniform emergence and stand.  There is no way that is going to be a negative to yield. Some other unknown factors are involved in those "test" if we take the data to be accurate.