For me, I would say that the magnitude of my attraction is roughly 50/50, but qualitatively, the attraction I feel towards a man is distinct from what I feel towards women.

A significant aspect that plays a role is also how I present to the world. From my appearance, most people would conclude that I am LGBTQ, and that usually means assuming I'm gay. This is useful because any bisexual's dating pool is biased towards opposite sex partners; if I want to find gay or bisexual (or pansexual or asexual) women to date, it's strategically useful to wear my sexuality on my sleeve, so to speak. This has the helpful side effects of filtering out the kind of straight asshole who says "why would you shave your hair like that? You might get more male attention if you made yourself look pretty"

Sexuality is messy. The attraction I feel is pretty equal. How the world perceives me is more gay than straight (because the world likes to pretend that bisexuality doesn't exist, and then act like I'm changing my mind when I "switch from being gay to straight" or vice versa (/facepalm). In terms of who I actually date or hook up with, the balance is probably skewed towards men. These three components (attraction, outward identification/presentation and behaviour) make sexuality complex, especially for bisexual people; I would wager that there are many people who identify as straight and have had no same sex relationships, but who experience some level of same-sex attraction. It also gets more complex when one considers that many people experience sexual attraction and romantic attraction differently. For example, I have a friend who is asexual, but homoromantic.

You might find it interesting to read about the Kinsey scale, which looks at sexuality as a spectrum, with exclusively [homosexual/heterosexual] on the extreme ends of the scale, and degrees of bisexuality between them.