Here is the amount of damage percentage that a hypothetical 30-power move of the type shown will do to the metagame on average from a Pokemon with 100 Attack and 100 Special Attack:
Average damage in the Standard metagame:
A Special Fire move will deal 74% more damage than a Special Poison move of the same power in Standard.
Average damage in the Underused metagame:
A Physical Rock move will deal 57% more damage than a Special Poison move of the same power in UU.
Average damage in the Uber metagame:
A Physical Dark move will deal 112% more damage (i.e. more than twice) than a Special Psychic move of the same power in ubers.
Average damage in the Standard metagame:

A Special Fire move will deal 74% more damage than a Special Poison move of the same power in Standard.
Average damage in the Underused metagame:

A Physical Rock move will deal 57% more damage than a Special Poison move of the same power in UU.
Average damage in the Uber metagame:

A Physical Dark move will deal 112% more damage (i.e. more than twice) than a Special Psychic move of the same power in ubers.