Precision 6870 for sale new . Only opened for photos

i would say it all depends on your main use of the car ...track or street ...typically a Detroit locker (trueurac) will yield more longevity and less maintenance ...there are pro's and cons of both depending on desired use ...research the two and see what you come up with...
I replaced the stock unit with an Eaton Tru Trac w/Moser 28 spline axles when the stocker wore out at about 79K miles . I Street drive and Track my car often. Low 10's car.
do i do the 28 spline or go to 30? its mainly a street car that we like to go to the track on midnight madness is mess with the kids here at Fort Campbell :)
I know a local guru that raced low 10s and eventually 9s for years with 28 spline. Don't shake the tires and it will last for what you are doing.
My opinion is based on daily driving a rock crawling trail rig up and down the canyons when we lived in Colorado.
My ‘85 S15 Jackal (so I dubbed it) was equipped with Powertrax Lockrites front and rear. They work the same as a Detroit Locker.

For a car that sees 75% street time I would choose the Detroit/ Eaton Trutrac.
For a car that sees less than 25% street time I would choose the Detroit Locker.

Here’s why.
There’s no differentiation while turning with a Detroit Locker.
When traveling straight both wheels are engaged (like a spool).
When turning, the over running wheel is disengaged and allowed to turn faster in relation to the pinion shaft.
In other words, when accelerating through a right turn, 100% of the power goes to the right wheel while the left wheel disengages and is allowed to coast (because it travels in a bigger circle) until enough power is applied to overpower the traction of the right tire. This will cause the right tire to spin until it catches up to the left tire and will continue to spin (similar to a spool) until traveling straight or power is reduced.

This is why, on a 4wd, it’s possible to drive while 3 tires are off the ground.

Because it’s a locking clog setup there’s no need for special posi additive like a clutch type limited slip or posi.

With a Trutrac, power is applied proportional to wheel speed on both sides while turning, the same as a limited slip or posi.
Since the Trutrac is a gear actuated limited slip it’s a more solid unit compared to the clutch type, there are no clutches to wear out and replace. There’s no need for special posi additive like a clutch type limited slip or posi either.

Just my feelings on the subject.

Photos just for fun.