I don't realy have an opinion on the ones in your list only cuz I never had any of them. I do use the DanaPowerlock in my front Dana44 and rear Dana60 and I love um!
This is how i was told the difference in traction differentials are:
1. Locker (both tires will spin at the same speed all the time)
2. Positraction (acts like an open diff until one tire looses traction or starts to spin way faster than the other then it is supose to redirect the torque to the slower spining tire. Somtime hitting the brake pedal is nessisary to get the torque to tranfer.
3. limited slip ( acts like a locker until the force/torque becomes too great on one tire compared to the other and will alow the tire to spin at a different speed or 'slip')
The Powerlock is considered a limitied slip, both tires will spin the same until the force, like turning a corner on dry pavement, makes the cluches slip.
I think it is important to have some kinda sliping up front when wheelin, that way you snap less parts.
Of corse all of this is based on what I have read and my own opinion so...............
oh ya a power lock is not cheap I think I paid 389 for my D44 one.
Good luck
72K5
Led Zeppelin
Rock ON!
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its all the same right? 
