Seeing as i'm pretty new to them, I got hooked onto them officially from their song 'STEP' Immediately Seungyeon caught my attention ^^ Shes just so adorable, and cute arghhh xD
But now i'm looking into Gyuri stuff, and absolutely love her, and her amazing witty humour xD
I must say though, if I was to choose a bias, it would NEVER be permanent, since every new thing I find out about the member makes me like them more xD