Everyone focuses on weighing the pegs. The key is locking your thigh into the tank. Pushing up off the pegs is just one way to get the thigh locked in. When you're in a corner, if you're pushing into the tank, the added weight while you're leaned is going to shove you farther into the tank.
It gets a lot harder in longer corners. Chuckwalla, for example, has a bowl corner that is 180 degrees and 11 degree banking. It's fast, and takes so long to get through you can grab a quick bite before exiting. Thing is I've never been able to stay locked in through the entire corner. On something like that I go with 50/50.
Pushing on the inside peg can loosen the rear tire if you twist the throttle enough or want to slide the rear. Otherwise, if you're a beginner rider, the only thing it really does is aid in putting pressure on the bars, which you shouldn't do.