I think that experience of self-discovery is different for everyone, because there are some different motivations for coming out as bisexual. Some people, like myself, simply have that attraction to both sexes inherent within them, and for me the discovery (or more accurately, coming to terms with that) was relatively slow. Others just do it for attention from boys, so for them the "discovery" is fast and the phase short-lived. I'm sure confusion is another common factor. I do believe that most have some sort of preference, yes. I find men and women equally beautiful, inside and out, but all else being equal, I'm going to go for the one with the penis.