18G will hold boost much better into high revs than the VF-52, or any IHI turbo for that matter.
It is torque that breaks transmissions, not power. An 18G can be tuned to ramp boost up at higher revs so as to flatten the torque curve and move peak torque higher up the rev range, which is kinder to the transmission. The VF-52 is a one-trick pony.. it does the big torque spike at around 3k5rpm and then falls off from there.
Terrible things like this don't happen where I come from. Other terrible things happen instead.
Obligatory 'build thread