Earth Ponies: Stronger than average, but have difficulties at operating complec machines, resulting in machines designed for ponies usually just having one big "on" and another big "off" button.
Pegasi: Weaker than Earth Ponies, but faster and can use wings for object manipulation (don´t ask, their wings evolved differently than bird wings) and flight. Some are even known to have broken the sound barrier.
Unicorns: Can use psionic abilities (AKA "magic") in order to manipulate objects, even weaker than Pegasi.
Alicorns: Extremely rare, these ponies feature wings as well as very strong psionic abilities, sometimes even strong enough to move celestial bodies, which is important to Equestrian culture, as both the planet Equestria as well as Equestria's moon are in unstable orbits held in place only be Alicorn powers.
Changelings: It is unknown how those insectoid beings similar to normal ponies came to be, but either way, they are capable of shape-shifting, flight and low levels of psionic manipulation. Their Queen is rumored to work for the EE secret service, which denies her employment fiercely.
New race: Mobians.
Measuring only about an average size of about 1 meter, their heads look rediculously large compared to their bodies, as they still feature a brain the size of a human's. They come in many sub-races which, surprisingly, are all interbreedable. There also is a lot of colour variation in the fur/feathers of Mobians.
Pic of King Elias Acorn, an average-looking Mobian who ruled the Republic of Acorn during the Second Robotnik War.
Spoiler:
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