Why does food cooked with peanut oil stick less than food cooked with sunflower oil?
I feel the same as you Anderson. I found that too and you just made me to do some research, which I found they have different smoke points.  

Unrefined sunflower oil 225°F   107°C
Unrefined peanut oil    320°F   160°C

see the link: http://www.cookingforengineers.com/article/50/Smoke-Points-of-Various-Fats

Also, one of the reasons food stick to the pan is the evenness of the temperature of the pan. If you use a thicker pan or copper pan, the heat will be distributed on the pan more evenly and food will stick less. The higher smoke point of oil makes me to believe the oil helps to distribute heat more evenly.