3/4 is more powerful. It is very easy my friend the power is expressed in freitions by rule and not write decimals. I explain so that the final fraction is not complicated is a division that is 3/4 refers to 3 divided by 4 which is equal 0.75.
3/8 refers to 3 divided by 8 which is equal to 0.375. Then 0.75 is greater than 0.375, therefore 3/4 represents greater power.
use calculator if you are not familiar with this and ready greetings