Here's something that no one ever mentions: The 9" pinion support. While it adds strength to the gear mesh, it takes up valuable room and forces design compromises in the limited slip. For that reason the 9" is much better suited to using either a spool or original type Detroit Locker. Those point towards strip use.
The 60, on the other hand, depends on the stiffness of the pinion shaft to keep the gears meshed. But there is plenty of room for a limited slip of about any configuration. This points towards street applications.
As far as weight goes, I don't think there's that much difference between a race 9" and a race D60. One is physically larger, for sure. That doesn't mean it's heavier when prepped for racing.
As far as limited slips go, the Truetrac has been developed over the last 30 years into a pretty decent unit. That's the direction I'd go in a hot street car, the D60 with Truetrac.
To me, nothing says "serious" like that odd-shaped differential cover. And there is something to be said for tradition, even though it doesn't win races.
