One advantage of Torx head bolts over hex bolts, is that the same torque head can be smaller in Torx. This is desirable for cars where a smaller bolt and drive

One advantage of Torx head bolts over hex bolts, is that the same torque head can be smaller in Torx. This is desirable for cars where a smaller bolt and driver (e-torx socket in this case) make access possible. So they can jam even more doohickeys into the engine bay.