I think its yeast, only because I used to pitch with dry yeast and I've now moved on to the "smack packs". Those same recipes I used to make with dry yeast have vastly improved with liquid yeast cultures.
"Beer is living proof that God loves us and wants us to be happy." Benjamin Franklin
Bottled: Cottage Coffee Stout Bottled: SuperBrew's Redheaded Stepchild Bottled: Gingerbread Ale Drinking: Most anything Thinking of: Apricot IPA