helical worm gearbox efficiency is much higher

worm gearbox manufacturers offer much higher than the worm gear. If you need a right angle solution with a low ratio the bevel gear is the right choice.
are used in low to moderate horsepower applications.
The helical worm gearbox offer low initial cost, high ratios, and high output torque in a small package. They have a much higher tolerance for shock loading then helical gear reducers. Helical reducers are used in higher horsepower applications where long-term operational efficiency is more important than initial cost.