Muslin cloths every single time. I have never used a bib. When my baby is sick on my shoulder (she has reflux), a bib just isn't going to cut it. When her hair is covered in ick, a bib just isn't going to cut it. A bib is useful when weaning I guess, and for those little dribbles of milk, but I wouldn't use one over a muslin which has uses far and beyond mopping up sick.