@desparil Well then, let me start... AHEM!
Why Unicorns are the master race. An scientific essay by the totally not racist AN602.
They can use magic. Obviously. They can cast all kinds of spells. And that's what makes Unicorns so extremely powerful compared to the two lesser tribes.
And magic is nothing but the purest energy. And the one who can make more use of energy, is always the stronger one. That counts for our universe as well.
And even if a Unicorn isn't nearly as gifted as Twilight Sparkle (pre-Alicorn), they still have their levitation spell. EVERY Unicorn is capable of casting that one. Even blank flanked fillies like Sweetie Belle can carry that off.
Anyway, even the levitation spell makes them superior to all the other tribes.
Y'all witnessed what Sweetie Belle did to Diamond Tiara.
Or Trixie. She bested all three races. Ok, Rarity didn't put up much of a fight.
The point is, a non-magic user is practically defenseless against any Unicorn.
Oh yeah, and Unicorns are even above Alicorns. For one simple reason:
There are exactly FOUR Alicorns currently alive.
How many Unicorns are there? Probably hundreds of millions.