My Roe rides the Ahriman simply because I find it incredibly ironic, given what background I know of her. She would never ride it ICly (I don't think anyway... ).
Besides that I normally use my coeurl, simply because I really don't like Chocobos, OOCly. If I had any RP scenes where my characters were to need a mount, they would use the Chocobo though, as they are what are commonly used to get around, and make the most sense for general use cases.
So I guess my real answer to this is that I really just seperate IC from OOC in the case of using mounts to get about the world. If RPing though, its best to abide by what makes sense for the scene/character!
Besides that I normally use my coeurl, simply because I really don't like Chocobos, OOCly. If I had any RP scenes where my characters were to need a mount, they would use the Chocobo though, as they are what are commonly used to get around, and make the most sense for general use cases.
So I guess my real answer to this is that I really just seperate IC from OOC in the case of using mounts to get about the world. If RPing though, its best to abide by what makes sense for the scene/character!