UniBalls are used because they're easy, they work, and when they're worn out they are common parts easily replaced. For street drivers they do have the liability of no dirt sealing, but if you maintain them as they need to be they'll have a reasonable service life. Dylan mentioned in the last go-round on this that Seals-It either has or is working on UniBall sealing washers (I don't recall which) which would go a long ways toward sealing dirt out.
Nothing against the AutoFab part as it is a superior piece. It's just a sole supplier part.
TS
"Teach you all I know and you're still stupid"
-- Howdy Lee