How the car was "broke-in" can have a lot to do with it as well.
If the car is driven hard when it's new, the engine tends to be looser than one that was driven a little more gently.
Unfortunately, their life expectancy isn't quite as long as one that was broke-in less aggressivly.
Now I'm not saying ALL engines that out perform their counterparts have been mistreated in their early lives. I'm just saying it can be a contributing factor in some cases.