Which font sizing is best? EM vs PX vs %

Here is what works for me... I set my font body to 72.5% at the body tag. So it looks something like this: body font-size:72.5% {in my CSS} then I can use: P {font-size:1.em} or whatever size you need.. you can even do 1.1em, 1.2em, 1.3em you get th…