When i got to know KARA for the first time through the MV "Mister", I thought Nicole was the leader back then.... She kind of gave that confident vibe xD
When I researched on them in wiki, I was kinda surprised ( idk why though ._.) that Gyuri was the leader. But after watching more shows of KARA, Gyuri indeed fits the leader role. Like everyone else said, she has a more mature image. I also like her wits and confidence!