My Summoner is going to be gaining the 'Greater Aspect' ability in a few levels. As I was looking over the evolutions that he could gain using these, I noticed the Breath Weapon and Frightful Presence evolutions. When the summoner grants these evolutions to himself, are his stats or his eidolon's stats used to determine how powerful they are?
I'm asking because if they use the eidolon's stats, that makes Breath Weapon potentially a powerful choice. However, if they use the summoner's stats, Frightful Presence suddenly becomes very powerful because of the summoner's higher HD and Cha. Yes, I know that the RAW text says "the eidolon's HD + Stat", but that just seems a little odd, doesn't it?
I suppose this question also applies to the 'Twin Eidolon' ability, since in a way the summoner becomes the eidolon, but keeps his level and mental stats. When the summoner is using Twin Eidolon, is his frightful presence more powerful than the Eidolon's? It would make sense in this case since the summoner has the eidolon's body, but is better able to cause fear with his higher CHA.