In my experience with the horses,they do have their own attitude and such.
For example my MFT is the best horse for me idk its because lucky or bought him with golds. But he really is my best horse,at one time i went to camp to cook something and as soon as i dismounted my MFT he went straight to the hitching pole and hitched himself. I was like wtf? He is so clever.
On the other hand my friend MFT is normal not to clever or to dumb.
Another horse that i can compare to my friend horse is Turkoman. While in the snow my Turkoman run like there is nothing in his feet,just go full speed. But my friend Turkoman run slower and both of us run at the same road covered with snow.
From that i believe that horses in RDO have different attitude although they are exactly the same.