Task: pros and cons of making chalk from one and cheese from another.
Favoritism is something that any company should try to avoid in the process of maintaining its workers, but who am I kidding? That's only theoretical, yet ought to be mandatory, statement proved to be useless in real world.
Lets take, for example, salary.. before (or after, which depends on various reasons) you're being interviewed you have a right to claim your future compensation package. It's not a favoritism yet, even though equal workers have different salary, but can evolve into one if worker with lower salary and bigger amount of work finds out yours.
Regardless of such manifestation of power this method allows proper allocation of resources due to simple thing: work more and you will get more. All you have to do as a manager is convey you message properly, so that every one understands it well.
It's not favoritism, you may say, but what would you answer were you on the lower salary man place?