You don't have to be "un-bullyable", you just have to be less bullyable than the next guy.
However, I still believe it's possible to fight back in a non-physical manner. My experience has always been that wit is sharper than fists, so I plan to teach my kids to fight back with language, not punches.
I attended 8 schools between ages 12 and 18 (yes, more than one per year) and was bullied throughout.
And that's why comparing parenting strategies is almost never fruitful -- nearly every decision a parent makes is deeply personal, made with very few data points.
( By the way, if any parents here have NOT read Nurture Shock, buy it right now. Pretty much the only data-driven book on parenting there is. http://www.amazon.com/dp/0446504122 )