I am looking at the difference between driders and centaurs monster type due to driders supposedly being a playable race in Pathfinder. However, driders are considered aberrations due essentially existing (being an exception to the far plane rule which somehow doesn't include cranium rats as an aberration). Same thing with Centaurs being monstrous creatures yet supposedly aren't scary or freakish to a majority of the pathfinder world for their origin(?). Is there really a major stat difference as well and that is why they are put in different categories?
Statistical differences include
- Hit die is d8 for Aberration vs d10 for M.H.
- BAB is 3/4 for Aberrations vs Full for M.H
- Saves: Aberrations have "Good" Will Saves while M.H. have "Good" Reflex and Will Saves (both have average for the unlisted Saves)
- Different Skills counted as "Class Skills"
Just as important are the descriptions of the creatures.
Aberrations are described
An aberration has a bizarre anatomy, strange abilities, an alien mindset, or any combination of the three. An aberration has the following features.
while Monstrous Humanoid are described
Monstrous humanoids are similar to humanoids, but with monstrous or animalistic features. They often have magical abilities as well. A monstrous humanoid has the following features.
By this description, Centaur might have been aberrations, but the fact that they came about in a natural way and their mindset being similar to that of the humanoid races suggests that M.H. is the better classification for them. Driders' unnatural origin makes the difference.
From the d20pfsrd:
Drider: Created from the body of a drow, warped and mutated through special poisons and elixirs to take on the characteristics of a giant spider, the drider is a dangerous creature.
Centaur: Legendary hunters and skilled warriors, centaurs are part man and part horse.
Going from those descriptions, I'd make the argument that Driders are an aberration because they are a departure from the norm and created via unnatural means. Centaurs are part of the natural world (they may have been initially created with the use of magic) but now procreate through purely biological means and "monsterous" to the eyes of the humanoid races.