Some balance.
Field replacement of a spoke is somewhat easier with straightpull as you don’t have to remove the disc.
Building a wheel is easy as long as you hold the spoke near the nipple when tightening the nipple (pliers with tape to not mark the spoke).
No windup when building / truing is an advantage. Spoke windup is a big problem for proper wheel building and spoke longevity. Simply relying on the J of a J bend spoke to hold against the rotation of the spoke is not good. Not knowing how much windup you have in a spoke is not good.
Stronger and stiffer (what percentage I dunno).