well, i have moral issues with chicken
I heard outside the EU farmers use a lot of hormones, which might not be so good for BBing - especially for a pubescent man. Its illegal to import any meat from the US into the EU for this very reason AFAIK.
The great thing about the powders is you can tailor the absorption properties - eg. whey absorbs extremely quickly and is gone in a few hours, whereas casien is slow. So you can use whey post workout for immediate effect and casien at night, so it lasts you through most of the time your asleep.
I dont know the absorption qualities of natural foods, although eggs + egg whites i think are medium speed, so they would be a good choice at bedtime - but they'll probably have burnt out a few hours before the morning, so a glass of milk or something as soon as you wake up will halt the catabolism.