[Gdeaver]

Chris,
You started this analysis looking to see if the Jags perceived linearity is a result of switching frequency alone. The discussion has evolved and now focused on what happens at the turn off. It's now apparent that there is a second major difference between the 3 controllers. The IFI 883 and 884 are low side switchers with a frequency of 120 and 2000. The jag is a high side switcher with a frequency of 15000. Al has pointed out that there is allot more going on because the h-bridge involves rotating magnetic fields and brush switching. So they have been ignored. Now, I can see your transient and current path at shut off. The low side D FET being on is the key since it is a low Resistance path. I Don't see where current would flow thru AL's path unless the transient is massive. Now I'm a little confused on the victor path.
The high side A Fet Is left on and the D Fet Turned off. The A-C side is left at vbat - the FET resistance. Where does the current flow? What happens on the B-D side. Seems to me the transient and back EMF would be clamped very fast By the high side on A fet. Do I have it right? So if I have this right
The IFI low side switcher decays fast and the jag high side switcher decays slower. Make sense? Now with the Jag the C FET diode bears the brunt of the off period current decay and with the IFI the A FET Bears the load but since it is on there is less stress. Make sense? Could this be a source of the jag failures? The Fet in the jag is not particularly designed for repetitive avalanche compared to some other fets. ( off topic but curious)
On the subject of controller linearity, IFI stated when they introduced the victor 884 that it gave better control in low duty cycle condition for controlling things like an arm where the motor maybe required to maintain a holding current. Now add in AL comments that there is allot more going on with the controller and motor than the simplified model in this discussion. Under real conditions, does the Jag maintain its linearity at low duty cycle conditions? Does the Jag trade controllability at high duty cycle rates and sacrifice the low end? Did IFI sacrifice the high for better control at the low end ? Al mentioned the word deterministic. These models can get nasty and complex real fast when all the variables are added in. At some point some real data will be needed to confirm this.