That is a hard one. I will just go with the ones I have.
Pink Skunks pair -- a subtle beauty to them. I really like how they "bark" at me if I am too close to the tank -- trying to act all tough.
SI Perc pair -- only have had them for a month, so not sure about their personality yet. But, sure like the colors of them. And like how fearless they are -- were eating out of my hand while in QT.
Clarkii pair -- Love/hate relationship. Have had them for about 9 years, and they have been through a lot, so like them for that. And I like how they will only chase my hand when I am removing it from the tank, not while it is in there. I guess that makes them feel like they were the reason I removed my hand. BUT, if they would ever go a day without fanning/digging in the sand I would be a happy person.