This is a hell of a poll. Karma to you.
As far as my choice, it is SATISFIED face over everything. With SMILEY face being 2nd.
Why I choose the SATISFIED face? I love the idea of a FBB enjoying being muscular and showing it off for anyone to see and nothing gives that impression better than the SATISFIED face. While the FBB is flexing it does 3 things.
1 - It makes the FBB look like she's getting off on her own physique.
2 - It makes the FBB look like she's getting off flexing her physique while others look on.
3 - It makes the FBB look like she's getting off on the fact that we are getting off on watching her.
It's not easy to pull off and very few women do it really well. Dena Westerfield, Alina Popa, Brandie Mae, Oana Hreapca, Kashma Maharaj, Lisa Giesbrecht, and Katka Kyptova are some good examples of women who are great at it.
SMILEY face is great as well because, like I said before, it helps the FBB give off the impression that she is truly enjoying showing off her muscles.
AGGRESSIVE face is too much like a put on for me. It's good to use in a contest routine but that is about it for me.
NEUTRAL face is just too bland. Makes the FBB look bored. Like she'd rather be doing something else.
BAD face can be hit or miss. Mostly a miss for me because once again, it makes the FBB look like they'd rather be somewhere else than showing off their muscles for my viewing pleasure.