For this sudden subject, let us start with the basic definition of the two nouns from the Free Dictionary.
Rival: One who attempts to equal or surpass another, or who pursues the same object as another.
Enemy: One feels hatred toward, intends injury to, or opposes another
This Literary Sentence sums it up the best:
It was, then, Richelieu’s object, not only to get rid of an enemy of France, but to avenge himself on a rival; but this vengeance must be grand and striking and worthy in every way of a man who held in his hand, as his weapon for combat, the forces of a kingdom.
– The Three Musketeers by Alexandre Dumas
So how do you compare what’s a rival and what’s an enemy in reality tv?
The two season of VH1 Scream Queens sums these up, like the 2 winners in both season.