These videos show that it isn't necessarily true:
To be honest, a lot of the perceived problems of the AR platform as Eugene Stoner were genuine issues in the original M-16 model. Things like the forward assist (which I personally used ONCE the very first time I shot an AR when I rode the charging handle home) have almost been engineered to extinction... Sun Devil and others make smooth-side upper receivers for a reason.
Is the AK a tougher platform? Certainly! Its built to very forgiving tolerances because it was built in very primitive factories by relatively unskilled labor.
Is the AK a better platform? That I can't answer, and I own both an AR (built from the stripped lower up, but a purchased complete upper).
But I have to say, the complete flexibility of the AR versus the AK is a huge bonus in my book.
(Originally seen at The Firearm Blog: AR-15 and AK-47 Dust Test)