My flowerhorn is very smart, with tons of personality.
My Oscar is smart, ornery, moody, pissed off, sulks, and is psycho.
On a very close vote I pick Flowerhorn.
I have to say O's out of the fish I've had, but I've seen some Midas that seemed pretty personable. I miss my O's, but like au duong phong said they do get boring when they are big. I always enjoyed when mid sized better.