Ok, so I'm going over my DM's head on this one.... this said I'm a DM so I never do this, and disdain the thought of it.
I'm playing a Cavalier. My DM is using the Horse Stats from the PF Core Rulebook. Should he not be using the stats AND Feats from the Bestiary?
I would think so. The idea is a Cavalier gets the Horse as written but with bonuses.
Now this said, add in the advanced template
http://www.d20pfsrd.com/bestiary/monster-listings/animals/horse/heavy-horse
Should this not be what a Cavalier starts with?!
A Heavy Horse, with bonuses so he is what the class is intended to be, a Knightly Horse Lord.
I'm playing according to my DMs ruling, and my horse with Chain Shirt Barding is almost so encumbered that it moves 35ft... less than a Barbarian. It is not nearly as strong as a heavy warhorse. so it is basically a wimp. Thankfuly it doesn't need feed to live.
It all seems so wrong for a class that does not cast spells like a Druid (uber-powerful) to suffer under pure druid animal-companion rulz :( :(
Hey look, I'm a Druid, my Horse is as good as yours Cavalier-horse-lord, and I cast uber-powerful spells.... u lose Cavalier.