If speech modulates a AM signal to a average of 30% then the same
speech will modulate a SSB to a similar reduced potential.

The efficiency of SSB over AM increases as the modulation decreases, approaching
infinity as the modulation and output approach zero. That's because even when
there is 0% modulation in AM you still have carrier power.

I stand corrected when running a mode below its maximum capability,
but if you are horse racing with the transmitters power rating being
equal between modes then this massive advantage disappears.
This would occur in a hors race, and when it does a SSB transmission
only has a 6db advantage over AM