Just in terms of looks? There's some apples/oranges in this as they have different strengths and weaknesses. Would you rather see a pretty girl who is bordering on fat (Sammi), or a less conventionally attractive face with really nice natural Cs and a flat stomach, but some unusual hip structure (Cindy...note I don't necessarily agree, but there are dissenters on Cindy's boobs, and it's true they cannot be considered perky), or a meh face/stumpy body but outrageously great and well-done fake Ds (michelle)?
I'd probably go Bibi Sammi Cindy Michelle. Factoring in my personal connection with them Cindy jumps to front for total experience, so: Cindy, Bibi, Sammi, Michelle.